ORIGINAL ARTICLE
Correlation Between EGFR Mutation Status and Computed Tomography Features in Patients With Advanced Pulmonary Adenocarcinoma Jui-Sheng Hsu, MD, PhD,*wz Ming-Shyan Huang, MD, PhD,y8 Chiao-Yun Chen, MD,*wz Gin-Chung Liu, MD, PhD,*wz Ta-Chih Liu, MD, PhD,z8 Inn-Wen Chong, MD,y8 Shah-Hwa Chou, MD,z and Chih-Jen Yang, MDy8#
Purpose: To correlate computed tomography (CT) imaging features and epidermal growth factor receptor (EGFR) mutation status in patients with advanced lung adenocarcinoma. Materials and Methods: Patients with advanced pulmonary adenocarcinoma who were diagnosed between January 1, 2009 and December 31, 2011 and who had available chest CT and their tumors analyzed for EGFR mutations at a university hospital were enrolled in this retrospective study. Two radiologists independently evaluated the CT images and recorded the target lesion’s size, shape, margin, density, and the presence or absence of an air bronchogram and calcification. Results: One hundred and forty-nine patients were enrolled into this study (66 men, 83 women), with a mean age of 63 ± 11 years (range 32 to 89 y). Seventy-eight (52.3%) patients had EGFR mutations. The tumors in the patients harboring no EGFR mutations (EGFR wild type) were larger than in those whose tumors harbored EGFR mutations (P = 0.01). An irregular shape was more common in the tumors with wild-type EGFR (P = 0.01), and an oval shape was more common in tumors with EGFR mutations. Tumors with exon 21 mutations were larger than those with exon 19 deletions (P = 0.02). Air bronchograms were more common in tumors with exon 19 deletions than in those with wild-type EGFR or exon 21 mutations (P = 0.004 and 0.01, respectively). Calcification was more common in the tumors with wild-type EGFR than in those with EGFR mutations (P = 0.03). Conclusions: Adenocarcinomas with wild-type EGFR were significantly associated with larger tumors and an irregular shape. In particular, calcification was more common in the tumors with wildtype EGFR than in those with EGFR mutations. In addition, air bronchograms were more common in the tumors with exon 19 deletions. Key Words: advanced lung adenocarcinoma, EGFR mutation, exon 19, calcification, chest computed tomography
(J Thorac Imaging 2014;29:357–363) From the *Department of Medical Imaging, Kaohsiung Medical University Hospital; wDepartment of Radiology, Faculty of Medicine, Graduate Institute of Medicine College of Medicine; zDivision of Hematology and Oncology; yDepartment of Internal Medicine, Division of Pulmonary and Critical Care Medicine; zDepartment of Surgery, Division of Chest Surgery; #Department of Internal Medicine, Kaohsiung Municipal Ta-Tung Hospital, Kaohsiung Medical University Hospital; and 8Faculty of Medicine, College of Medicine, Kaohsiung Medical University, Taiwan. This study was supported by a grant from the Kaohsiung Medical University Hospital (KMUH99-9R09). The authors declare no conflicts of interest. Reprints: Chih-Jen Yang, MD, Department of Internal Medicine, Kaohsiung Municipal Ta-Tung Hospital, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Kaohsiung City, #100, Tzyou 1st Road, Kaohsiung 807, Taiwan (e-mail: [email protected]). Copyright r 2014 by Lippincott Williams & Wilkins
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E
pidermal growth factor receptor (EGFR) is a transmembrane receptor tyrosine kinase involved in the signaling pathways that regulate cell proliferation, apoptosis, angiogenesis, and invasion.1–4 Prior studies have shown that patients with pulmonary adenocarcinoma with EGFR mutations respond well to EGFR tyrosine kinase inhibitors (TKI).5–7 EGFR mutations are correlated with nonsmoking status, female sex, East Asians, and adenocarcinomas.1,2,4,8,9 EGFR mutations with exon 19 deletions and L858R point mutation in exon 21 occur most frequently and are associated with a high response rate of approximately 70% to EGFRTKI therapy, and the progression-free survival has been reported to be up to 9 to 13 months if EGFR-TKIs are used as the first-line therapy.1,2,4,8,10–14 Imaging plays an important role in diagnosis and response assessment in cases of lung cancer. However, only a few published studies have specifically evaluated the correlation of the radiologic appearance of pulmonary adenocarcinoma and EGFR mutation status.15–18 Pulmonary adenocarcinomas with a dominant ground-glass opacity (GGO) have often been reported to possess EGFR mutations.3,17 Choi et al reported that smaller nodular lesions, peripheral lesions, and exon 19 deletions were related to a better response to EGFR-TKI therapy.17 To date, most studies have focused on early-stage and resectable lung cancer. In this study, we correlated the relationship between computed tomography (CT) features and mutation status in patients with advanced adenocarcinomas (stage IIIB and stage IV).
MATERIALS AND METHODS Patient Selection This study was approved by our Institutional Review Board as a retrospective study, and the requirement for patient informed consent was waived. Patients with advanced pulmonary adenocarcinoma who were diagnosed between January 1, 2009 and December 31, 2011 and who had their tumors analyzed for EGFR mutations at a university hospital were enrolled in this study. The inclusion criteria were an available pathologic report for EGFR mutations and preoperative CT images on radiology using the Picture Archiving and Communication System (PACS, EBM). The exclusion criteria included insufficient pathologic specimens for EGFR mutation examinations, unavailable initial CT images, and a duration of >3 months between the CT imaging and the subsequent surgery or core biopsy. One hundred forty-nine patients (63 ± 11 y; age range 32 to 89 y; 66 men and 83 women) were included in this www.thoracicimaging.com |
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study (Table 1). All patients were Taiwanese. Ten patents were excluded because CT imaging was not available on the hospital PACS. All specimens were obtained from CTguided biopsy, bronchoscopic biopsy, or surgical specimens. All of these patients had successful EGFR test results. The lung cancer stages according to the seventh edition of the Union for International Cancer Control and American Joint Committee on Cancer TNM classification were stage IIIB in 15 patients (10.1%) and stage IV in 134 (89.9%).
Direct Sequence of EGFR Mutational Analysis Direct sequencing is widely used for EGFR mutation detection and remains the gold standard for gene mutation analysis.19,20 Formalin-fixed, paraffin-embedded tissue blocks were used for DNA analysis. Tumor areas were identified in routine sections and stained with hematoxylin and eosin. Two to 4 unstained sections (10 mm thick) from each paraffin-embedded wax specimen were obtained for DNA extraction. Four separate polymerase chain reactions (PCR) with the corresponding pair of primers were used to amplify exons 18 to 21 of the EGFR gene.20 The PCR products were purified using a Gel/PCR DNA fragment extraction kit (GENEAID). Direct sequencing was performed on a 3130xl Genetic Analyzer (Applied Biosystems), and the samples were analyzed using GeneScan 3.1 software (Applied Biosystems). All mutations were confirmed by sequences originating from both the upstream and downstream primers. Common sensitive EGFR mutations were L858R point mutation in exon 21 and an in-frame deletion mutation in exon 19. Exon 18 mutations are rare, and exon 20 mutations are nonsense or resistant.
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CT Imaging CT imaging was performed using 1 of 3 CT systems (LightSpeed Ultra16, GE Medical Systems, Milwaukee, WI; Sensation 16, Siemens Medical Systems, SOMATOM Definition Flash, Germany; and Brilliance 64, Philips Medical Systems, Haifa, Israel) for 132 (88.6%) patients at our hospital and for 17 (11.4%) at outside hospitals. The CT parameters were as follows: LightSpeed Ultra16, GE Medical Systems (1.25 mm collimation, pitch of 1.375, rotation time 0.8 s, 120 kVp, 300 mAs, contiguous 5-mmthick sections, and 1.25 mm thickness and 5 mm intervals in high-resolution lung image), Sensation 16, Siemens Medical Systems (0.6 mm collimation, pitch of 1.2, rotation time 0.5 s, 120 kVp, 110 mAs, contiguous 5-mm-thick sections, and 1 mm thickness and 5 mm intervals in high-resolution lung image), Brilliance 64, Philip Medical Systems (0.625 mm collimation, pitch of 1.078, rotation time 0.75 s, 120 kVp, 250 mAs, contiguous 5-mm-thickness sections, and 1 mm thickness and 5 mm interval in high-resolution lung image). Image reconstruction parameters were contiguous 5-mm-thick sections and non-contiguous, highresolution lung images (1 mm thickness and 5 mm interval) in 85 (57%) patients, contiguous 5-mm-thick sections and non-contiguous, high-resolution lung images (1.25 mm thickness and 5 mm interval) in 47 (31.5%) patients, and contiguous 5-mm-thick sections in 17 (11.4%) patients. Each CT image covered the lower neck to the level of the adrenal glands. One hundred twenty-five (83.9%) patients were examined by CT after enhancement with an intravenous contrast medium. The median time between diagnostic CT scanning and obtaining the specimen was 8.9 ± 4.5 days (range 3 to 21 d).
TABLE 1. Basic Characteristics and EGFR Mutation Status of All Patients with Advanced Pulmonary Adenocarcinoma
Patient Characteristics (n = 149) No. patients Sex Male Female Age (y) [mean (range)] Male Female Smoking status Nonsmoker Smoker Tumor size (cm) [mean (range)] TNM stage [n (%)] IIIB IV T stage [n (%)] T1 T2 T3 T4 N stage [n (%)] N0 N1 N2 N3 M stage [n (%)] M0 M1
Overall
Wild-type
EGFR Mutation
149
71 (47.7)
78 (52.3)
66 83
34 (51.5) 37 (44.6)
32 (48.5) 46 (55.4)
63 (33-85) 63 (33-88)
64 (47-89) 62 (32-86)
38 (53.5) 33 (46.5) 4.7 (1.3-13.4)
54 (69.2) 24 (30.8) 3.7 (1.2-10.5)
7 (9.9) 64 (90.1)
13 (16.7) 65 (83.3)
36 47 17 39
18 21 10 22
(25.4) (29.6) (14.1) (31)
18 36 7 17
(23.1) (46.2) (9) (21.8)
10 16 53 70
5 3 25 38
(7) (4.2) (35.2) (53.5)
5 13 28 32
(6.4) (16.7) (35.9) (41)
P 0.41 0.94
149 20 129
0.01* 0.22 0.19
0.09
0.22 20 129
7 (9.9) 64 (90.1)
13 (16.7) 65 (83.3)
*P < 0.05. P value was based on a comparison between EGFR mutation status and sex, age, tumor size, and TMN stage.
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Two radiologists independently interpreted the CT images for the target lesions. Both radiologists were aware that the patients had lung adenocarcinomas but were unaware of the pathologic reports and the results of EGFR status. Radiologic parameters such as lesion size, shape, margin, density, air bronchograms, and calcifications were recorded for each patient. If their interpretations were different, a joint session was held to reach a final decision by consensus. Lesion size was assessed as the maximal diameter of the target lesion. Lesion shape was categorized as round, oval, lobular, and irregular. Round was defined as spherical or circular, and oval as elliptical or egg-shaped, which may include 2 or 3 undulations, that is, “gently lobulated” or “macrolobulated.” Lobulated was defined as >3 undulations, and irregular was defined as neither round, oval, nor lobulated in shape.21 The lesion margin was categorized as circumscribed, microlobulated, angular, spiculated, and obscured, modified from nodule lexicon of BI-RADS.21 A circumscribed margin was defined as a margin that was smooth and well defined between the lesion and surrounding tissue. Not circumscribed was defined as a mass having 1 or more of the following features: microlobulated, angular, spiculated, and obscured. Microlobulated was defined as short-cycle (usually 1 to 2 mm) undulations imparting a scalloped appearance to the margin of the mass. An angular margin was defined as some or the entire margin having sharp corners, often forming acute angles. A spiculated margin was characterized by sharp lines projecting from the mass, and an obscured margin was defined as the target margin being hidden by superimposed adjacent tissue, such as a tumor being enclosed by pneumonia, and when CT images
Correlation Between EGFR Mutation and CT in Patients With Lung Cancer
were difficult to evaluate for the tumor margin either on contrast or noncontrast imaging. The priority of the lesion margin was ordered as spiculated, angular, microlobulated, obscured, and circumscribed (Figs. 1A–F). Lesion density was categorized as GGO, mixed GGO, and solid on CT. GGO was defined as a hazy increase in lung opacity with preservation of bronchial and vascular markings on noncontrast CT. Mixed GGO was defined as a solid part within the GGO, and a solid lesion was defined as a 3-dimensional solid space-occupying lesion. Air bronchograms on CT images were defined as small foci or branching bands of air attenuation within the solid part of either mixed or solid lesions (Fig. 2A). Air bronchograms were excluded from pneumonia where possible. Calcification in a pulmonary nodule on imaging indicates a high probability that the lesion is benign. However, not all calcified pulmonary nodules are benign. Amorphous, punctate, isolated flecks, and reticular patterns of calcification have been described in lung cancer.22 Calcification on CT images was defined as the presence of highdensity material in the lesion unexplained by artifacts on nonenhanced CT images (Fig. 2B). Differences between the 2 readers in the interpretation of the shape categorization (6 of 149 nodules, 4%) and margin categorization (9 of 149 nodules, 6%) were resolved by discussion until a consensus was reached.
Statistical Analysis The variables were presented as mean ± SD, and the Shapiro Wilks normality test was used to determine whether the data were normally distributed. Unpaired t tests were used for normally distributed variables, and Kruskal-Wallis variance analysis and Mann-Whitney U tests were used for
FIGURE 1. A, A well-circumscribed round stage IV adenocarcinoma with wild-type EGFR in a 47-year-old man. B, A microlobulated oval stage IV adenocarcinoma with exon 18 insertion in a 62-year-old man. C, An angular, irregular stage IV adenocarcinoma with wild-type EGFR in a 55-year-old man. D, An angular, irregular stage IV adenocarcinoma with wild-type EGFR in a 55-year-old man. E, A spiculated, irregular stage IV adenocarcinoma with wild-type EGFR in a 57-year-old man. F, A well-circumscribed, lobulated stage IV adenocarcinoma with exon 21 point mutation in a 56-year-old woman. r
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FIGURE 2. A, Air bronchograms in stage IV adenocarcinoma with 19 deletions in a 48-year-old man. B, Reticular calcification in stage IV adenocarcinoma with wild-type EGFR in a 76-year-old woman.
non-normally distributed variables. The Fisher exact test and the Pearson w2 test were used for nominal variables. Binomial logistic regression analysis and Kruskal-Wallis variance analysis were performed to test associations between EGFR mutations and morphologic CT features with adjustments for other factors. A P value of 2 samples that are independent or not related. The parametric equivalent of the Kruskal-Wallis test is the 1-way analysis of variance. When the Kruskal-Wallis test leads to significant results, then at least 1 of the samples is different from the other samples. The test does not identify where the differences occur or how many differences actually occur. The Fisher exact test and the Pearson w2 test are statistical significance tests used in the analysis of contingency tables for comparisons in subgroups to identify where the differences occur.
RESULTS Seventy-eight of 149 (52.3%) adenocarcinomas showed EGFR mutations: exon 21, L858R, missense mutation in 31 (20.8%), exon 19 deletions in 40 (26.8%), exon 18 deletion or missense in 4 (2.7%), and exon 20 insertion in 3 (2.0%). Age was a normally distributed variable in this study. No differences were found with regard to
sex and age between adenocarcinomas with wild-type EGFR and those with EGFR mutations (Tables 1, 2, 3). Nonsmokers have a trend to be associated with adenocarcinomas with EGFR mutations rather than those with wild-type EGFR, although the difference was not statistically significant (P = 0.06) (Table 3). Tumor size was not a normally distributed variable in this study. Adenocarcinomas with wild-type EGFR (4.7 ± 2.6 cm, range 1.3 to 13.4 cm) were larger than those with EGFR mutations (3.7 ± 1.9 cm, range 1.2 to 10.5 cm) (P = 0.01) and those with exon 19 deletions (3.2 ± 1.7 cm, range 1.2 to 10.2 cm) (P < 0.001) (Table 4). Adenocarcinomas with exon 21 missense (4.2 ± 2.1 cm, range 1.5 to 10.5 cm) were larger than those with exon 19 deletions (P = 0.02). An oval shape was more common in adenocarcinomas with EGFR mutations than in those with wild-type EGFR (P = 0.04). An irregular shape was more common in adenocarcinomas with wild-type EGFR than in those with EGFR mutations (P = 0.01) (Table 5). No significant differences were found in the appearance of lesion density, margin, and air bronchograms between adenocarcinomas with wild-type EGFR and those with EGFR mutations. However, air bronchograms were more common in adenocarcinomas with exon 19 deletions than in those with wild-type EGFR (P = 0.004) and in those with exon 21 mutations (P = 0.01) (Table 6). Calcification was more common in adenocarcinomas with wild-type EGFR than in those with EGFR mutations (P = 0.03) and in those with exon 21 mutations (P = 0.03). However, no significant differences were found with regard to calcification between adenocarcinomas with wild-type EGFR and those with exon 19 deletions (P = 0.11) or
TABLE 2. Sex According to EGFR Mutation Subtype
Subtype Wild-type Exon 19 deletion Exon 21 mutation Exon 18 deletion or missense Exon 20 insertion
Total (n = 149) 71 40 31 4 3
Women (n = 83) 37 21 20 3 2
Men (n = 66)
(52.1) (52.5) (64.5) (75) (66.7)
34 19 21 1 1
(47.9) (47.5) (35.5) (25) (33.3)
P 0.41
Data are represented as numbers with percentages. Statistical comparison was performed using the Fisher exact test. P value was based on a comparison between adenocarcinomas with wide-type EGFR and with all EGFR mutations (P = 0.41) and with exon 19 deletion (P = 1.0) and 21 missense (P = 0.28).
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TABLE 3. Smoking Status According to EGFR Mutation Subtype
Subtype
Total (n = 149)
Wild-type Exon 19 deletion Exon 21 mutation Exon 18 deletion or missense Exon 20 insertion
Nonsmoker (n = 92)
71 40 31 4 3
38 25 24 3 2
Smoker (n = 57)
(53.5) (62.5) (77.4) (75) (66.7)
33 15 7 1 1
(46.5) (37.5) (22.6) (25) (33.3)
P 0.06
Data are represented as numbers with percentages. Statistical comparison was performed using the Fisher exact test. P value was based on comparison between adenocarcinomas with wide-type EGFR and with EGFR mutations (P = 0.06), exon 19 deletion (P = 0.43), and 21 missense (P = 0.07). Adenocarcinomas with exon 18 deletion or missense and with exon 20 insertion were not included in EGFR-subgroups statistics because of small numbers.
between adenocarcinomas with exon 19 deletions and those with exon 21 mutations (P = 0.63) (Table 6).
DISCUSSION Lung cancer is the leading cause of cancer deaths worldwide, and it is also the leading cancer site in males, comprising 17% of the new cancer cases and 23% of total cancer deaths.23 The majority of lung cancer patients have non–small cell lung cancer (NSCLC), and adenocarcinoma is the most common subtype of NSCLC.24,25 In a recent metaanalysis study, EGFR-TKI therapy was found to statistically and significantly delay disease progression in patients with EGFR mutations; this study concluded that TKIs should be considered as the front-line therapy in patients with advanced adenocarcinoma harboring EGFR mutations.26 Importantly, EGFR-TKI therapy has been demonstrated to have efficacy in the treatment of advanced pulmonary adenocarcinoma harboring EGFR mutations. In addition, NSCLC patients with exon 19 deletions have been reported to survive for longer after gefitinib treatment than those with exon 21 point mutations.27,28 Our results showed that EGFR mutations were not associated with sex, age, or nonsmoking status. Prior clinical studies of EGFR mutations in NSCLC have reported a higher frequency in women with adenocarcinoma, among a younger age group, in East Asians, and in nonsmokers.29 However, other studies have reported no associations between the presence of EGFR mutations and sex or age.15,30 Differences may exist between these studies related to selection bias due to the heterogenous pathologic profiles of the patients. In addition, we found that 52.3% of the selected patients with pulmonary adenocarcinoma harbored EGFR mutations, which is consistent with previous reports.29
Regarding the correlation between EGFR mutation status and CT features, our results revealed that air bronchograms were more frequently seen in adenocarcinomas with EGFR mutations than wild-type EGFR, which is consistent with previous studies.31 Bronchioloalveolar carcinoma (BAC) features have been used to describe the lepidic spread of lung adenocarcinoma.22,32 However, BAC has been used to describe a clinicopathologic correlation between BAC with BAC features and EGFR mutations. Previous studies have shown correlations among adenocarcinomas with EGFR mutations, BAC, and BAC features.16 Radiologically, adenocarcinoma in situ appears as GGO. In the analysis of serial changes of GGO on CT imaging, localized GGO can change into mixed GGO and solid attenuation.33 The central solid region of mixed GGO implies an invasive component, and GGO has frequently been found in adenocarcinomas with EGFR mutations on CT imaging.16,34 In addition, air bronchograms and air alveolograms are other characteristic signs of BAC features. Pathologically, these signs are due to unrestricted bronchiolar lumens and alveoli, in contrast to adenocarcinoma in situ. In our study, air bronchograms were more frequently found in adenocarcinomas with exon 19 deletions, and only a small number of cases with mixed GGO lesions were found because most of the patients already had advanced lung cancer. These results are different from those described by Lee et al,16 who reported that air bronchograms were more frequent in exon 21 missense and exon 21 mutations and more frequent in lepidic-predominant adenocarcinomas before an advanced stage. The prevalence of calcified lung cancers identified on conventional chest radiographs has been reported to be 1%.22 Modern CT scanners have a much higher sensitivity, which has led to an increased prevalence of 6% to 10% of calcification in lung cancers.22 Patterns of calcification in cancers include punctate, amorphous, and reticular, in a
TABLE 4. Tumor Size According to EGFR Mutation Subtype
Tumor Size Subtype
Total (n = 149)
Wild-type Exon 19 deletion Exon 21 missense Exon 18 deletion or missense Exon 20 insertion
71 40 31 4 3
1.1-2 cm (n = 21) 11 9 1 0
(15.5) (22.5) (3.2) (0) 0
2.1-3 cm (n = 38) 9 17 11 1
(12.7) (42.5) (35.5) (25) 0
> 3 cm (n = 90) 51 14 19 3 3
(71.8) (35.0) (61.3) (75) (100)
P 0.01
Data are represented as numbers with percentages. Tumor size was a non-normally distributed variable. The statistical comparison was performed using a Mann-Whitney U test. P values were based on a comparison between adenocarcinomas with wide-type EGFR and with EGFR mutations (P = 0.01), exon 19 deletion (P < 0.01), and 21 missense (P = 0.33). Adenocarcinomas with exon 21 missense was larger than those with exon 19 deletions (P = 0.02). Adenocarcinomas with exon 18 deletion or missense and with exon 20 insertion were not included in the EGFR-subgroups statistics because of small numbers.
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TABLE 5. CT Features According to EGFR Mutation Subtype
Morphologic CT Features Shape Round Oval Lobulated Irregular Density Mixed GGO Solid Margin Circumscribed Microlobulated Angular Spiculated Obscured
Wild-type (n = 71)
Exon 19 Deletion (n = 40)
Exon 21 Point Mutation (n = 31)
Exon 18 Deletion or Missense (n = 4)
Exon 20 Insertion (n = 3)
P 0.04*
3 13 25 35
(4.2) (18.3) (28.2) (49.3)
2 15 14 9
(5) (37.5) (35) (22.5)
2 9 11 9
(6.5) (29) (35.5) (29)
0 2 0 2
(0) (50) (0) (50)
0 0 1 2
(0) (0) (33.3) (66.7)
2 (2.8) 69 (97.2)
1 (2.5) 39 (97.5)
0 (0) 31 (100)
0 (0) 4 (100)
0 (0) 3 (100)
27 9 22 4 9
17 3 11 4 5
10 7 7 1 6
1 2 1 0 0
0 1 1 1 0
0.04w 0.60w 0.01w 0.88* 0.84*
(38) (12.7) (31) (5.6) (12.7)
(42.5) (7.5) (27.5) (10) (12.5)
(32.3) (22.6) (22.6) (3.2) (19.4)
(25) (50) (25) (0) (0)
(0) (33.3) (33.3) (33.3) (0)
Data are represented as numbers with percentages. Statistical comparisons were performed by using the Kruskal-Wallis test* and the Fisher testw. Adenocarcinomas with a round-shape were not included in shape-subgroups statistics because of the small numbers. *P value was based on a comparison between adenocarcinomas with wide-type EGFR and with EGFR mutations with regard to shape, density, and margin of adenocarcinomas. wP value was based on a comparison between adenocarcinomas with wide-type EGFR and with EGFR mutations with regard to shape-subgroups of adenocarcinomas.
decreasing order of frequency. Calcification in primary lung cancers has been proposed to have different mechanisms ranging from engulfment of calcified scar tissue, degenerated bronchial cartilage, and granulomatous processes engulfing the tumor to dystrophic calcification in areas of tumor necrosis. Calcification may also develop as sequelae to chemotherapy or in association with hypercalcemia. Calcium deposition may also occur as the result of a secretory function of the carcinoma itself (eg, mucinous carcinoma).22 We found that adenocarcinomas with wildtype EGFR were significantly associated with calcifications compared with those with EGFR mutations. To the best of our knowledge, this finding has not been previously reported. Adenocarcinoma with EGFR mutations is considered to be critical in the pathogenesis of nonmucinous BAC tumors but not in mucinous BAC-type tumors. This may explain why so little calcification was seen in the adenocarcinomas with EGFR mutations. Our results revealed that advanced lung adenocarcinomas with wild-type EGFR were larger than those with EGFR mutations. In addition, we found that an irregular shape was more common in the adenocarcinomas with
wild-type EGFR, and an oval shape was more common in adenocarcinomas with EGFR mutations. However, there are a number of limitations to this study that need to be highlighted. First, our sample size was relatively small. Our final study population was smaller than the initially identified group because some patients did not have preoperative imaging studies available at our institution. Second, sample bias may exist because EGFR mutations are only routinely analyzed in patients with stage IIIB or stage IV and not for early-stage lung cancer at our institution. Third, our study only correlated CT imaging and EGFR mutation status in advanced adenocarcinomas and not CT imaging and histologic IASLC/ATS/ERS classification of lung adenocarcinoma. Further studies are necessary to elucidate this issue. Fourth, the method of testing for EGFR mutations in our institution was direct sequencing. In fact, direct sequencing is widely used for EGFR mutation detection and remains the gold standard for gene mutation analysis, although it has low sensitivity. The method requires that at least 50% of assayed cells are malignant, corresponding to mutations in approximately 25% of the total DNA in the sample.19 Fifth, our study did
TABLE 6. Air Bronchograms and Calcification According to EGFR Mutation Subtype
Subtype Air bronchograms (n = 34) Calcifications (n = 19)
Wild-type (n = 71)
Exon 19 Deletion (n = 40)
Exon 21 Missense (n = 31)
Exon 18 Deletion or Missense (n = 4)
Exon 20 Insertion (n = 3)
P
12 (16.9)
17 (42.5)
4 (12.9)
0 (0)
1 (33.3)
0.12*
14 (19.7)
3 (9.5)
1 (3.2)
1 (25)
0 (0)
0.03w
*P values were based on comparisons between adenocarcinomas with EGFR wide-type and with all EGFR mutations (P = 0.12), exon 19 deletion (P = 0.004) and 21 missense (P = 0.77) in air bronchogram. wP values were based on comparisons between adenocarcinomas with EGFR wide-type and with all EGFR mutations (P = 0.03), exon 19 deletion (P = 0.11) and 21 missense (P = 0.03) in calcification Adenocarcinomas with exon 18 deletion or missense, and with exon 20 insertion were not include in EGFR-subgroups statistics because of small numbers.
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not check for KRAS mutations, and a KRAS mutation has been reported to be unsuitable for EGFR-TKI therapy.16,35 Further studies are necessary to elucidate this issue. Finally, we did not correlate CT imaging and progression-free survival and overall survival in this study. In summary, we found a correlation between advanced lung adenocarcinomas with EGFR status and certain CT imaging features. Adenocarcinomas with wild-type EGFR were significantly associated with larger tumors, irregular shape, and calcifications in CT imaging. Air bronchograms were more common in tumors with exon 19 deletions. REFERENCES 1. Herbst RS, Heymach JV, Lippman SM. Lung cancer. N Engl J Med. 2008;359:1367–1380. 2. Nishino M, Hatabu H, Johnson BE, et al. State of the art: response assessment in lung cancer in the era of genomic medicine. Radiology. 2014;271:6–27. 3. Nishino M, Jackman DM, Hatabu H, et al. Imaging of lung cancer in the era of molecular medicine. Acad Radiol. 2011;18:424–436. 4. Gazdar AF. Personalized medicine and inhibition of EGFR signaling in lung cancer. N Engl J Med. 2009;361:1018–1020. 5. Lynch TJ, Bell DW, Sordella R, et al. Activating mutations in the epidermal growth factor receptor underlying responsiveness of non-small-cell lung cancer to gefitinib. N Engl J Med. 2004;350:2129–2139. 6. Paez JG, Janne PA, Lee JC, et al. EGFR mutations in lung cancer: correlation with clinical response to gefitinib therapy. Science. 2004;304:1497–1500. 7. Pao W, Miller V, Zakowski M, et al. EGF receptor gene mutations are common in lung cancers from “never smokers” and are associated with sensitivity of tumors to gefitinib and erlotinib. Proc Natl Acad Sci USA. 2004;101:13306–13311. 8. Maemondo M, Inoue A, Kobayashi K, et al. Gefitinib or chemotherapy for non-small-cell lung cancer with mutated EGFR. N Engl J Med. 2010;362:2380–2388. 9. Usuda K, Sagawa M, Motono N, et al. Relationships between EGFR mutation status of lung cancer and preoperative factors are they predictive? Asian Pac J Cancer Prev. 2014;15:657–662. 10. Mok TS, Wu YL, Thongprasert S, et al. Gefitinib or carboplatin-paclitaxel in pulmonary adenocarcinoma. N Engl J Med. 2009;361:947–957. 11. Rosell R, Carcereny E, Gervais R, et al. Erlotinib versus standard chemotherapy as first-line treatment for European patients with advanced EGFR mutation-positive non-smallcell lung cancer (EURTAC): a multicentre, open-label, randomised phase 3 trial. Lancet Oncol. 2012;13:239–246. 12. Thunnissen E, van der Oord K, den BM. Prognostic and predictive biomarkers in lung cancer. A review. Virchows Arch. 2014;464:347–358. 13. Zhou C, Wu YL, Chen G, et al. Erlotinib versus chemotherapy as first-line treatment for patients with advanced EGFR mutation-positive non-small-cell lung cancer (OPTIMAL, CTONG-0802): a multicentre, open-label, randomised, phase 3 study. Lancet Oncol. 2011;12:735–742. 14. Sequist LV, Martins RG, Spigel D, et al. First-line gefitinib in patients with advanced non-small-cell lung cancer harboring somatic EGFR mutations. J Clin Oncol. 2008;26:2442–2449. 15. Haneda H, Sasaki H, Lindeman N, et al. A correlation between EGFR gene mutation status and bronchioloalveolar carcinoma features in Japanese patients with adenocarcinoma. Jpn J Clin Oncol. 2006;36:69–75. 16. Lee HJ, Kim YT, Kang CH, et al. Epidermal growth factor receptor mutation in lung adenocarcinomas: relationship with CT characteristics and histologic subtypes. Radiology. 2013;268:254–264.
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17. Choi CM, Kim MY, Lee JC, et al. Advanced lung adenocarcinoma harboring a mutation of the epidermal growth factor receptor: CT findings after tyrosine kinase inhibitor therapy. Radiology. 2014;270:574–582. 18. Onn A, Choe DH, Herbst RS, et al. Tumor cavitation in stage I non-small cell lung cancer: epidermal growth factor receptor expression and prediction of poor outcome. Radiology. 2005; 237:342–347. 19. Jung CY. Biopsy and mutation detection strategies in nonsmall cell lung cancer. Tuberc Respir Dis (Seoul). 2013;75: 181–187. 20. Togashi Y, Masago K, Kubo T, et al. Association of diffuse, random pulmonary metastases, including miliary metastases, with epidermal growth factor receptor mutations in lung adenocarcinoma. Cancer. 2011;117:819–825. 21. Obenauer S, Hermann KP, Grabbe E. Applications and literature review of the BI-RADS classification. Eur Radiol. 2005;15:1027–1036. 22. Khan AN, Al-Jahdali HH, Allen CM, et al. The calcified lung nodule: what does it mean? Ann Thorac Med. 2010;5:67–79. 23. Jemal A, Bray F, Center MM, et al. Global cancer statistics. CA Cancer J Clin. 2011;61:69–90. 24. Travis WD, Travis LB, Devesa SS. Lung cancer. Cancer. 1995;75:191–202. 25. Auerbach O, Garfinkel L. The changing pattern of lung carcinoma. Cancer. 1991;68:1973–1977. 26. Lee CK, Brown C, Gralla RJ, et al. Impact of EGFR inhibitor in non-small cell lung cancer on progression-free and overall survival: a meta-analysis. J Natl Cancer Inst. 2013;105: 595–605. 27. Jackman DM, Yeap BY, Sequist LV, et al. Exon 19 deletion mutations of epidermal growth factor receptor are associated with prolonged survival in non-small cell lung cancer patients treated with gefitinib or erlotinib. Clin Cancer Res. 2006;12:3908–3914. 28. Zhu JQ, Zhong WZ, Zhang GC, et al. Better survival with EGFR exon 19 than exon 21 mutations in gefitinib-treated non-small cell lung cancer patients is due to differential inhibition of downstream signals. Cancer Lett. 2008;265: 307–317. 29. Hsieh RK, Lim KH, Kuo HT, et al. Female sex and bronchioloalveolar pathologic subtype predict EGFR mutations in non-small cell lung cancer. Chest. 2005;128: 317–321. 30. Jang TW, Oak CH, Chang HK, et al. EGFR and KRAS mutations in patients with adenocarcinoma of the lung. Korean J Intern Med. 2009;24:48–54. 31. Tsao AS, Tang XM, Sabloff B, et al. Clinicopathologic characteristics of the EGFR gene mutation in non-small cell lung cancer. J Thorac Oncol. 2006;1:231–239. 32. Travis WD, Brambilla E, Noguchi M, et al. International association for the study of lung cancer/american thoracic society/european respiratory society international multidisciplinary classification of lung adenocarcinoma. J Thorac Oncol. 2011;6:244–285. 33. Yanagawa M, Kuriyama K, Kunitomi Y, et al. One-dimensional quantitative evaluation of peripheral lung adenocarcinoma with or without ground-glass opacity on thin-section CT images using profile curves. Br J Radiol. 2009;82:532–540. 34. Aoki T, Hanamiya M, Uramoto H, et al. Adenocarcinomas with predominant ground-glass opacity: correlation of morphology and molecular biomarkers. Radiology. 2012;264: 590–596. 35. van ZN, Mathy A, Boerrigter L, et al. EGFR and KRAS mutations as criteria for treatment with tyrosine kinase inhibitors: retro- and prospective observations in non-smallcell lung cancer. Ann Oncol. 2007;18:99–103.
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Correlation Between EGFR Mutation Status and Computed Tomography Features in Patients With Advanced Pulmonary Adenocarcinoma Jui-Sheng Hsu, MD, PhD,*wz Ming-Shyan Huang, MD, PhD,y8 Chiao-Yun Chen, MD,*wz Gin-Chung Liu, MD, PhD,*wz Ta-Chih Liu, MD, PhD,z8 Inn-Wen Chong, MD,y8 Shah-Hwa Chou, MD,z and Chih-Jen Yang, MDy8#
Purpose: To correlate computed tomography (CT) imaging features and epidermal growth factor receptor (EGFR) mutation status in patients with advanced lung adenocarcinoma. Materials and Methods: Patients with advanced pulmonary adenocarcinoma who were diagnosed between January 1, 2009 and December 31, 2011 and who had available chest CT and their tumors analyzed for EGFR mutations at a university hospital were enrolled in this retrospective study. Two radiologists independently evaluated the CT images and recorded the target lesion’s size, shape, margin, density, and the presence or absence of an air bronchogram and calcification. Results: One hundred and forty-nine patients were enrolled into this study (66 men, 83 women), with a mean age of 63 ± 11 years (range 32 to 89 y). Seventy-eight (52.3%) patients had EGFR mutations. The tumors in the patients harboring no EGFR mutations (EGFR wild type) were larger than in those whose tumors harbored EGFR mutations (P = 0.01). An irregular shape was more common in the tumors with wild-type EGFR (P = 0.01), and an oval shape was more common in tumors with EGFR mutations. Tumors with exon 21 mutations were larger than those with exon 19 deletions (P = 0.02). Air bronchograms were more common in tumors with exon 19 deletions than in those with wild-type EGFR or exon 21 mutations (P = 0.004 and 0.01, respectively). Calcification was more common in the tumors with wild-type EGFR than in those with EGFR mutations (P = 0.03). Conclusions: Adenocarcinomas with wild-type EGFR were significantly associated with larger tumors and an irregular shape. In particular, calcification was more common in the tumors with wildtype EGFR than in those with EGFR mutations. In addition, air bronchograms were more common in the tumors with exon 19 deletions. Key Words: advanced lung adenocarcinoma, EGFR mutation, exon 19, calcification, chest computed tomography
(J Thorac Imaging 2014;29:357–363) From the *Department of Medical Imaging, Kaohsiung Medical University Hospital; wDepartment of Radiology, Faculty of Medicine, Graduate Institute of Medicine College of Medicine; zDivision of Hematology and Oncology; yDepartment of Internal Medicine, Division of Pulmonary and Critical Care Medicine; zDepartment of Surgery, Division of Chest Surgery; #Department of Internal Medicine, Kaohsiung Municipal Ta-Tung Hospital, Kaohsiung Medical University Hospital; and 8Faculty of Medicine, College of Medicine, Kaohsiung Medical University, Taiwan. This study was supported by a grant from the Kaohsiung Medical University Hospital (KMUH99-9R09). The authors declare no conflicts of interest. Reprints: Chih-Jen Yang, MD, Department of Internal Medicine, Kaohsiung Municipal Ta-Tung Hospital, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Kaohsiung City, #100, Tzyou 1st Road, Kaohsiung 807, Taiwan (e-mail: [email protected]). Copyright r 2014 by Lippincott Williams & Wilkins
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E
pidermal growth factor receptor (EGFR) is a transmembrane receptor tyrosine kinase involved in the signaling pathways that regulate cell proliferation, apoptosis, angiogenesis, and invasion.1–4 Prior studies have shown that patients with pulmonary adenocarcinoma with EGFR mutations respond well to EGFR tyrosine kinase inhibitors (TKI).5–7 EGFR mutations are correlated with nonsmoking status, female sex, East Asians, and adenocarcinomas.1,2,4,8,9 EGFR mutations with exon 19 deletions and L858R point mutation in exon 21 occur most frequently and are associated with a high response rate of approximately 70% to EGFRTKI therapy, and the progression-free survival has been reported to be up to 9 to 13 months if EGFR-TKIs are used as the first-line therapy.1,2,4,8,10–14 Imaging plays an important role in diagnosis and response assessment in cases of lung cancer. However, only a few published studies have specifically evaluated the correlation of the radiologic appearance of pulmonary adenocarcinoma and EGFR mutation status.15–18 Pulmonary adenocarcinomas with a dominant ground-glass opacity (GGO) have often been reported to possess EGFR mutations.3,17 Choi et al reported that smaller nodular lesions, peripheral lesions, and exon 19 deletions were related to a better response to EGFR-TKI therapy.17 To date, most studies have focused on early-stage and resectable lung cancer. In this study, we correlated the relationship between computed tomography (CT) features and mutation status in patients with advanced adenocarcinomas (stage IIIB and stage IV).
MATERIALS AND METHODS Patient Selection This study was approved by our Institutional Review Board as a retrospective study, and the requirement for patient informed consent was waived. Patients with advanced pulmonary adenocarcinoma who were diagnosed between January 1, 2009 and December 31, 2011 and who had their tumors analyzed for EGFR mutations at a university hospital were enrolled in this study. The inclusion criteria were an available pathologic report for EGFR mutations and preoperative CT images on radiology using the Picture Archiving and Communication System (PACS, EBM). The exclusion criteria included insufficient pathologic specimens for EGFR mutation examinations, unavailable initial CT images, and a duration of >3 months between the CT imaging and the subsequent surgery or core biopsy. One hundred forty-nine patients (63 ± 11 y; age range 32 to 89 y; 66 men and 83 women) were included in this www.thoracicimaging.com |
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study (Table 1). All patients were Taiwanese. Ten patents were excluded because CT imaging was not available on the hospital PACS. All specimens were obtained from CTguided biopsy, bronchoscopic biopsy, or surgical specimens. All of these patients had successful EGFR test results. The lung cancer stages according to the seventh edition of the Union for International Cancer Control and American Joint Committee on Cancer TNM classification were stage IIIB in 15 patients (10.1%) and stage IV in 134 (89.9%).
Direct Sequence of EGFR Mutational Analysis Direct sequencing is widely used for EGFR mutation detection and remains the gold standard for gene mutation analysis.19,20 Formalin-fixed, paraffin-embedded tissue blocks were used for DNA analysis. Tumor areas were identified in routine sections and stained with hematoxylin and eosin. Two to 4 unstained sections (10 mm thick) from each paraffin-embedded wax specimen were obtained for DNA extraction. Four separate polymerase chain reactions (PCR) with the corresponding pair of primers were used to amplify exons 18 to 21 of the EGFR gene.20 The PCR products were purified using a Gel/PCR DNA fragment extraction kit (GENEAID). Direct sequencing was performed on a 3130xl Genetic Analyzer (Applied Biosystems), and the samples were analyzed using GeneScan 3.1 software (Applied Biosystems). All mutations were confirmed by sequences originating from both the upstream and downstream primers. Common sensitive EGFR mutations were L858R point mutation in exon 21 and an in-frame deletion mutation in exon 19. Exon 18 mutations are rare, and exon 20 mutations are nonsense or resistant.
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CT Imaging CT imaging was performed using 1 of 3 CT systems (LightSpeed Ultra16, GE Medical Systems, Milwaukee, WI; Sensation 16, Siemens Medical Systems, SOMATOM Definition Flash, Germany; and Brilliance 64, Philips Medical Systems, Haifa, Israel) for 132 (88.6%) patients at our hospital and for 17 (11.4%) at outside hospitals. The CT parameters were as follows: LightSpeed Ultra16, GE Medical Systems (1.25 mm collimation, pitch of 1.375, rotation time 0.8 s, 120 kVp, 300 mAs, contiguous 5-mmthick sections, and 1.25 mm thickness and 5 mm intervals in high-resolution lung image), Sensation 16, Siemens Medical Systems (0.6 mm collimation, pitch of 1.2, rotation time 0.5 s, 120 kVp, 110 mAs, contiguous 5-mm-thick sections, and 1 mm thickness and 5 mm intervals in high-resolution lung image), Brilliance 64, Philip Medical Systems (0.625 mm collimation, pitch of 1.078, rotation time 0.75 s, 120 kVp, 250 mAs, contiguous 5-mm-thickness sections, and 1 mm thickness and 5 mm interval in high-resolution lung image). Image reconstruction parameters were contiguous 5-mm-thick sections and non-contiguous, highresolution lung images (1 mm thickness and 5 mm interval) in 85 (57%) patients, contiguous 5-mm-thick sections and non-contiguous, high-resolution lung images (1.25 mm thickness and 5 mm interval) in 47 (31.5%) patients, and contiguous 5-mm-thick sections in 17 (11.4%) patients. Each CT image covered the lower neck to the level of the adrenal glands. One hundred twenty-five (83.9%) patients were examined by CT after enhancement with an intravenous contrast medium. The median time between diagnostic CT scanning and obtaining the specimen was 8.9 ± 4.5 days (range 3 to 21 d).
TABLE 1. Basic Characteristics and EGFR Mutation Status of All Patients with Advanced Pulmonary Adenocarcinoma
Patient Characteristics (n = 149) No. patients Sex Male Female Age (y) [mean (range)] Male Female Smoking status Nonsmoker Smoker Tumor size (cm) [mean (range)] TNM stage [n (%)] IIIB IV T stage [n (%)] T1 T2 T3 T4 N stage [n (%)] N0 N1 N2 N3 M stage [n (%)] M0 M1
Overall
Wild-type
EGFR Mutation
149
71 (47.7)
78 (52.3)
66 83
34 (51.5) 37 (44.6)
32 (48.5) 46 (55.4)
63 (33-85) 63 (33-88)
64 (47-89) 62 (32-86)
38 (53.5) 33 (46.5) 4.7 (1.3-13.4)
54 (69.2) 24 (30.8) 3.7 (1.2-10.5)
7 (9.9) 64 (90.1)
13 (16.7) 65 (83.3)
36 47 17 39
18 21 10 22
(25.4) (29.6) (14.1) (31)
18 36 7 17
(23.1) (46.2) (9) (21.8)
10 16 53 70
5 3 25 38
(7) (4.2) (35.2) (53.5)
5 13 28 32
(6.4) (16.7) (35.9) (41)
P 0.41 0.94
149 20 129
0.01* 0.22 0.19
0.09
0.22 20 129
7 (9.9) 64 (90.1)
13 (16.7) 65 (83.3)
*P < 0.05. P value was based on a comparison between EGFR mutation status and sex, age, tumor size, and TMN stage.
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Two radiologists independently interpreted the CT images for the target lesions. Both radiologists were aware that the patients had lung adenocarcinomas but were unaware of the pathologic reports and the results of EGFR status. Radiologic parameters such as lesion size, shape, margin, density, air bronchograms, and calcifications were recorded for each patient. If their interpretations were different, a joint session was held to reach a final decision by consensus. Lesion size was assessed as the maximal diameter of the target lesion. Lesion shape was categorized as round, oval, lobular, and irregular. Round was defined as spherical or circular, and oval as elliptical or egg-shaped, which may include 2 or 3 undulations, that is, “gently lobulated” or “macrolobulated.” Lobulated was defined as >3 undulations, and irregular was defined as neither round, oval, nor lobulated in shape.21 The lesion margin was categorized as circumscribed, microlobulated, angular, spiculated, and obscured, modified from nodule lexicon of BI-RADS.21 A circumscribed margin was defined as a margin that was smooth and well defined between the lesion and surrounding tissue. Not circumscribed was defined as a mass having 1 or more of the following features: microlobulated, angular, spiculated, and obscured. Microlobulated was defined as short-cycle (usually 1 to 2 mm) undulations imparting a scalloped appearance to the margin of the mass. An angular margin was defined as some or the entire margin having sharp corners, often forming acute angles. A spiculated margin was characterized by sharp lines projecting from the mass, and an obscured margin was defined as the target margin being hidden by superimposed adjacent tissue, such as a tumor being enclosed by pneumonia, and when CT images
Correlation Between EGFR Mutation and CT in Patients With Lung Cancer
were difficult to evaluate for the tumor margin either on contrast or noncontrast imaging. The priority of the lesion margin was ordered as spiculated, angular, microlobulated, obscured, and circumscribed (Figs. 1A–F). Lesion density was categorized as GGO, mixed GGO, and solid on CT. GGO was defined as a hazy increase in lung opacity with preservation of bronchial and vascular markings on noncontrast CT. Mixed GGO was defined as a solid part within the GGO, and a solid lesion was defined as a 3-dimensional solid space-occupying lesion. Air bronchograms on CT images were defined as small foci or branching bands of air attenuation within the solid part of either mixed or solid lesions (Fig. 2A). Air bronchograms were excluded from pneumonia where possible. Calcification in a pulmonary nodule on imaging indicates a high probability that the lesion is benign. However, not all calcified pulmonary nodules are benign. Amorphous, punctate, isolated flecks, and reticular patterns of calcification have been described in lung cancer.22 Calcification on CT images was defined as the presence of highdensity material in the lesion unexplained by artifacts on nonenhanced CT images (Fig. 2B). Differences between the 2 readers in the interpretation of the shape categorization (6 of 149 nodules, 4%) and margin categorization (9 of 149 nodules, 6%) were resolved by discussion until a consensus was reached.
Statistical Analysis The variables were presented as mean ± SD, and the Shapiro Wilks normality test was used to determine whether the data were normally distributed. Unpaired t tests were used for normally distributed variables, and Kruskal-Wallis variance analysis and Mann-Whitney U tests were used for
FIGURE 1. A, A well-circumscribed round stage IV adenocarcinoma with wild-type EGFR in a 47-year-old man. B, A microlobulated oval stage IV adenocarcinoma with exon 18 insertion in a 62-year-old man. C, An angular, irregular stage IV adenocarcinoma with wild-type EGFR in a 55-year-old man. D, An angular, irregular stage IV adenocarcinoma with wild-type EGFR in a 55-year-old man. E, A spiculated, irregular stage IV adenocarcinoma with wild-type EGFR in a 57-year-old man. F, A well-circumscribed, lobulated stage IV adenocarcinoma with exon 21 point mutation in a 56-year-old woman. r
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FIGURE 2. A, Air bronchograms in stage IV adenocarcinoma with 19 deletions in a 48-year-old man. B, Reticular calcification in stage IV adenocarcinoma with wild-type EGFR in a 76-year-old woman.
non-normally distributed variables. The Fisher exact test and the Pearson w2 test were used for nominal variables. Binomial logistic regression analysis and Kruskal-Wallis variance analysis were performed to test associations between EGFR mutations and morphologic CT features with adjustments for other factors. A P value of 2 samples that are independent or not related. The parametric equivalent of the Kruskal-Wallis test is the 1-way analysis of variance. When the Kruskal-Wallis test leads to significant results, then at least 1 of the samples is different from the other samples. The test does not identify where the differences occur or how many differences actually occur. The Fisher exact test and the Pearson w2 test are statistical significance tests used in the analysis of contingency tables for comparisons in subgroups to identify where the differences occur.
RESULTS Seventy-eight of 149 (52.3%) adenocarcinomas showed EGFR mutations: exon 21, L858R, missense mutation in 31 (20.8%), exon 19 deletions in 40 (26.8%), exon 18 deletion or missense in 4 (2.7%), and exon 20 insertion in 3 (2.0%). Age was a normally distributed variable in this study. No differences were found with regard to
sex and age between adenocarcinomas with wild-type EGFR and those with EGFR mutations (Tables 1, 2, 3). Nonsmokers have a trend to be associated with adenocarcinomas with EGFR mutations rather than those with wild-type EGFR, although the difference was not statistically significant (P = 0.06) (Table 3). Tumor size was not a normally distributed variable in this study. Adenocarcinomas with wild-type EGFR (4.7 ± 2.6 cm, range 1.3 to 13.4 cm) were larger than those with EGFR mutations (3.7 ± 1.9 cm, range 1.2 to 10.5 cm) (P = 0.01) and those with exon 19 deletions (3.2 ± 1.7 cm, range 1.2 to 10.2 cm) (P < 0.001) (Table 4). Adenocarcinomas with exon 21 missense (4.2 ± 2.1 cm, range 1.5 to 10.5 cm) were larger than those with exon 19 deletions (P = 0.02). An oval shape was more common in adenocarcinomas with EGFR mutations than in those with wild-type EGFR (P = 0.04). An irregular shape was more common in adenocarcinomas with wild-type EGFR than in those with EGFR mutations (P = 0.01) (Table 5). No significant differences were found in the appearance of lesion density, margin, and air bronchograms between adenocarcinomas with wild-type EGFR and those with EGFR mutations. However, air bronchograms were more common in adenocarcinomas with exon 19 deletions than in those with wild-type EGFR (P = 0.004) and in those with exon 21 mutations (P = 0.01) (Table 6). Calcification was more common in adenocarcinomas with wild-type EGFR than in those with EGFR mutations (P = 0.03) and in those with exon 21 mutations (P = 0.03). However, no significant differences were found with regard to calcification between adenocarcinomas with wild-type EGFR and those with exon 19 deletions (P = 0.11) or
TABLE 2. Sex According to EGFR Mutation Subtype
Subtype Wild-type Exon 19 deletion Exon 21 mutation Exon 18 deletion or missense Exon 20 insertion
Total (n = 149) 71 40 31 4 3
Women (n = 83) 37 21 20 3 2
Men (n = 66)
(52.1) (52.5) (64.5) (75) (66.7)
34 19 21 1 1
(47.9) (47.5) (35.5) (25) (33.3)
P 0.41
Data are represented as numbers with percentages. Statistical comparison was performed using the Fisher exact test. P value was based on a comparison between adenocarcinomas with wide-type EGFR and with all EGFR mutations (P = 0.41) and with exon 19 deletion (P = 1.0) and 21 missense (P = 0.28).
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TABLE 3. Smoking Status According to EGFR Mutation Subtype
Subtype
Total (n = 149)
Wild-type Exon 19 deletion Exon 21 mutation Exon 18 deletion or missense Exon 20 insertion
Nonsmoker (n = 92)
71 40 31 4 3
38 25 24 3 2
Smoker (n = 57)
(53.5) (62.5) (77.4) (75) (66.7)
33 15 7 1 1
(46.5) (37.5) (22.6) (25) (33.3)
P 0.06
Data are represented as numbers with percentages. Statistical comparison was performed using the Fisher exact test. P value was based on comparison between adenocarcinomas with wide-type EGFR and with EGFR mutations (P = 0.06), exon 19 deletion (P = 0.43), and 21 missense (P = 0.07). Adenocarcinomas with exon 18 deletion or missense and with exon 20 insertion were not included in EGFR-subgroups statistics because of small numbers.
between adenocarcinomas with exon 19 deletions and those with exon 21 mutations (P = 0.63) (Table 6).
DISCUSSION Lung cancer is the leading cause of cancer deaths worldwide, and it is also the leading cancer site in males, comprising 17% of the new cancer cases and 23% of total cancer deaths.23 The majority of lung cancer patients have non–small cell lung cancer (NSCLC), and adenocarcinoma is the most common subtype of NSCLC.24,25 In a recent metaanalysis study, EGFR-TKI therapy was found to statistically and significantly delay disease progression in patients with EGFR mutations; this study concluded that TKIs should be considered as the front-line therapy in patients with advanced adenocarcinoma harboring EGFR mutations.26 Importantly, EGFR-TKI therapy has been demonstrated to have efficacy in the treatment of advanced pulmonary adenocarcinoma harboring EGFR mutations. In addition, NSCLC patients with exon 19 deletions have been reported to survive for longer after gefitinib treatment than those with exon 21 point mutations.27,28 Our results showed that EGFR mutations were not associated with sex, age, or nonsmoking status. Prior clinical studies of EGFR mutations in NSCLC have reported a higher frequency in women with adenocarcinoma, among a younger age group, in East Asians, and in nonsmokers.29 However, other studies have reported no associations between the presence of EGFR mutations and sex or age.15,30 Differences may exist between these studies related to selection bias due to the heterogenous pathologic profiles of the patients. In addition, we found that 52.3% of the selected patients with pulmonary adenocarcinoma harbored EGFR mutations, which is consistent with previous reports.29
Regarding the correlation between EGFR mutation status and CT features, our results revealed that air bronchograms were more frequently seen in adenocarcinomas with EGFR mutations than wild-type EGFR, which is consistent with previous studies.31 Bronchioloalveolar carcinoma (BAC) features have been used to describe the lepidic spread of lung adenocarcinoma.22,32 However, BAC has been used to describe a clinicopathologic correlation between BAC with BAC features and EGFR mutations. Previous studies have shown correlations among adenocarcinomas with EGFR mutations, BAC, and BAC features.16 Radiologically, adenocarcinoma in situ appears as GGO. In the analysis of serial changes of GGO on CT imaging, localized GGO can change into mixed GGO and solid attenuation.33 The central solid region of mixed GGO implies an invasive component, and GGO has frequently been found in adenocarcinomas with EGFR mutations on CT imaging.16,34 In addition, air bronchograms and air alveolograms are other characteristic signs of BAC features. Pathologically, these signs are due to unrestricted bronchiolar lumens and alveoli, in contrast to adenocarcinoma in situ. In our study, air bronchograms were more frequently found in adenocarcinomas with exon 19 deletions, and only a small number of cases with mixed GGO lesions were found because most of the patients already had advanced lung cancer. These results are different from those described by Lee et al,16 who reported that air bronchograms were more frequent in exon 21 missense and exon 21 mutations and more frequent in lepidic-predominant adenocarcinomas before an advanced stage. The prevalence of calcified lung cancers identified on conventional chest radiographs has been reported to be 1%.22 Modern CT scanners have a much higher sensitivity, which has led to an increased prevalence of 6% to 10% of calcification in lung cancers.22 Patterns of calcification in cancers include punctate, amorphous, and reticular, in a
TABLE 4. Tumor Size According to EGFR Mutation Subtype
Tumor Size Subtype
Total (n = 149)
Wild-type Exon 19 deletion Exon 21 missense Exon 18 deletion or missense Exon 20 insertion
71 40 31 4 3
1.1-2 cm (n = 21) 11 9 1 0
(15.5) (22.5) (3.2) (0) 0
2.1-3 cm (n = 38) 9 17 11 1
(12.7) (42.5) (35.5) (25) 0
> 3 cm (n = 90) 51 14 19 3 3
(71.8) (35.0) (61.3) (75) (100)
P 0.01
Data are represented as numbers with percentages. Tumor size was a non-normally distributed variable. The statistical comparison was performed using a Mann-Whitney U test. P values were based on a comparison between adenocarcinomas with wide-type EGFR and with EGFR mutations (P = 0.01), exon 19 deletion (P < 0.01), and 21 missense (P = 0.33). Adenocarcinomas with exon 21 missense was larger than those with exon 19 deletions (P = 0.02). Adenocarcinomas with exon 18 deletion or missense and with exon 20 insertion were not included in the EGFR-subgroups statistics because of small numbers.
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TABLE 5. CT Features According to EGFR Mutation Subtype
Morphologic CT Features Shape Round Oval Lobulated Irregular Density Mixed GGO Solid Margin Circumscribed Microlobulated Angular Spiculated Obscured
Wild-type (n = 71)
Exon 19 Deletion (n = 40)
Exon 21 Point Mutation (n = 31)
Exon 18 Deletion or Missense (n = 4)
Exon 20 Insertion (n = 3)
P 0.04*
3 13 25 35
(4.2) (18.3) (28.2) (49.3)
2 15 14 9
(5) (37.5) (35) (22.5)
2 9 11 9
(6.5) (29) (35.5) (29)
0 2 0 2
(0) (50) (0) (50)
0 0 1 2
(0) (0) (33.3) (66.7)
2 (2.8) 69 (97.2)
1 (2.5) 39 (97.5)
0 (0) 31 (100)
0 (0) 4 (100)
0 (0) 3 (100)
27 9 22 4 9
17 3 11 4 5
10 7 7 1 6
1 2 1 0 0
0 1 1 1 0
0.04w 0.60w 0.01w 0.88* 0.84*
(38) (12.7) (31) (5.6) (12.7)
(42.5) (7.5) (27.5) (10) (12.5)
(32.3) (22.6) (22.6) (3.2) (19.4)
(25) (50) (25) (0) (0)
(0) (33.3) (33.3) (33.3) (0)
Data are represented as numbers with percentages. Statistical comparisons were performed by using the Kruskal-Wallis test* and the Fisher testw. Adenocarcinomas with a round-shape were not included in shape-subgroups statistics because of the small numbers. *P value was based on a comparison between adenocarcinomas with wide-type EGFR and with EGFR mutations with regard to shape, density, and margin of adenocarcinomas. wP value was based on a comparison between adenocarcinomas with wide-type EGFR and with EGFR mutations with regard to shape-subgroups of adenocarcinomas.
decreasing order of frequency. Calcification in primary lung cancers has been proposed to have different mechanisms ranging from engulfment of calcified scar tissue, degenerated bronchial cartilage, and granulomatous processes engulfing the tumor to dystrophic calcification in areas of tumor necrosis. Calcification may also develop as sequelae to chemotherapy or in association with hypercalcemia. Calcium deposition may also occur as the result of a secretory function of the carcinoma itself (eg, mucinous carcinoma).22 We found that adenocarcinomas with wildtype EGFR were significantly associated with calcifications compared with those with EGFR mutations. To the best of our knowledge, this finding has not been previously reported. Adenocarcinoma with EGFR mutations is considered to be critical in the pathogenesis of nonmucinous BAC tumors but not in mucinous BAC-type tumors. This may explain why so little calcification was seen in the adenocarcinomas with EGFR mutations. Our results revealed that advanced lung adenocarcinomas with wild-type EGFR were larger than those with EGFR mutations. In addition, we found that an irregular shape was more common in the adenocarcinomas with
wild-type EGFR, and an oval shape was more common in adenocarcinomas with EGFR mutations. However, there are a number of limitations to this study that need to be highlighted. First, our sample size was relatively small. Our final study population was smaller than the initially identified group because some patients did not have preoperative imaging studies available at our institution. Second, sample bias may exist because EGFR mutations are only routinely analyzed in patients with stage IIIB or stage IV and not for early-stage lung cancer at our institution. Third, our study only correlated CT imaging and EGFR mutation status in advanced adenocarcinomas and not CT imaging and histologic IASLC/ATS/ERS classification of lung adenocarcinoma. Further studies are necessary to elucidate this issue. Fourth, the method of testing for EGFR mutations in our institution was direct sequencing. In fact, direct sequencing is widely used for EGFR mutation detection and remains the gold standard for gene mutation analysis, although it has low sensitivity. The method requires that at least 50% of assayed cells are malignant, corresponding to mutations in approximately 25% of the total DNA in the sample.19 Fifth, our study did
TABLE 6. Air Bronchograms and Calcification According to EGFR Mutation Subtype
Subtype Air bronchograms (n = 34) Calcifications (n = 19)
Wild-type (n = 71)
Exon 19 Deletion (n = 40)
Exon 21 Missense (n = 31)
Exon 18 Deletion or Missense (n = 4)
Exon 20 Insertion (n = 3)
P
12 (16.9)
17 (42.5)
4 (12.9)
0 (0)
1 (33.3)
0.12*
14 (19.7)
3 (9.5)
1 (3.2)
1 (25)
0 (0)
0.03w
*P values were based on comparisons between adenocarcinomas with EGFR wide-type and with all EGFR mutations (P = 0.12), exon 19 deletion (P = 0.004) and 21 missense (P = 0.77) in air bronchogram. wP values were based on comparisons between adenocarcinomas with EGFR wide-type and with all EGFR mutations (P = 0.03), exon 19 deletion (P = 0.11) and 21 missense (P = 0.03) in calcification Adenocarcinomas with exon 18 deletion or missense, and with exon 20 insertion were not include in EGFR-subgroups statistics because of small numbers.
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not check for KRAS mutations, and a KRAS mutation has been reported to be unsuitable for EGFR-TKI therapy.16,35 Further studies are necessary to elucidate this issue. Finally, we did not correlate CT imaging and progression-free survival and overall survival in this study. In summary, we found a correlation between advanced lung adenocarcinomas with EGFR status and certain CT imaging features. Adenocarcinomas with wild-type EGFR were significantly associated with larger tumors, irregular shape, and calcifications in CT imaging. Air bronchograms were more common in tumors with exon 19 deletions. REFERENCES 1. Herbst RS, Heymach JV, Lippman SM. Lung cancer. N Engl J Med. 2008;359:1367–1380. 2. Nishino M, Hatabu H, Johnson BE, et al. State of the art: response assessment in lung cancer in the era of genomic medicine. Radiology. 2014;271:6–27. 3. Nishino M, Jackman DM, Hatabu H, et al. Imaging of lung cancer in the era of molecular medicine. Acad Radiol. 2011;18:424–436. 4. Gazdar AF. Personalized medicine and inhibition of EGFR signaling in lung cancer. N Engl J Med. 2009;361:1018–1020. 5. Lynch TJ, Bell DW, Sordella R, et al. Activating mutations in the epidermal growth factor receptor underlying responsiveness of non-small-cell lung cancer to gefitinib. N Engl J Med. 2004;350:2129–2139. 6. Paez JG, Janne PA, Lee JC, et al. EGFR mutations in lung cancer: correlation with clinical response to gefitinib therapy. Science. 2004;304:1497–1500. 7. Pao W, Miller V, Zakowski M, et al. EGF receptor gene mutations are common in lung cancers from “never smokers” and are associated with sensitivity of tumors to gefitinib and erlotinib. Proc Natl Acad Sci USA. 2004;101:13306–13311. 8. Maemondo M, Inoue A, Kobayashi K, et al. Gefitinib or chemotherapy for non-small-cell lung cancer with mutated EGFR. N Engl J Med. 2010;362:2380–2388. 9. Usuda K, Sagawa M, Motono N, et al. Relationships between EGFR mutation status of lung cancer and preoperative factors are they predictive? Asian Pac J Cancer Prev. 2014;15:657–662. 10. Mok TS, Wu YL, Thongprasert S, et al. Gefitinib or carboplatin-paclitaxel in pulmonary adenocarcinoma. N Engl J Med. 2009;361:947–957. 11. Rosell R, Carcereny E, Gervais R, et al. Erlotinib versus standard chemotherapy as first-line treatment for European patients with advanced EGFR mutation-positive non-smallcell lung cancer (EURTAC): a multicentre, open-label, randomised phase 3 trial. Lancet Oncol. 2012;13:239–246. 12. Thunnissen E, van der Oord K, den BM. Prognostic and predictive biomarkers in lung cancer. A review. Virchows Arch. 2014;464:347–358. 13. Zhou C, Wu YL, Chen G, et al. Erlotinib versus chemotherapy as first-line treatment for patients with advanced EGFR mutation-positive non-small-cell lung cancer (OPTIMAL, CTONG-0802): a multicentre, open-label, randomised, phase 3 study. Lancet Oncol. 2011;12:735–742. 14. Sequist LV, Martins RG, Spigel D, et al. First-line gefitinib in patients with advanced non-small-cell lung cancer harboring somatic EGFR mutations. J Clin Oncol. 2008;26:2442–2449. 15. Haneda H, Sasaki H, Lindeman N, et al. A correlation between EGFR gene mutation status and bronchioloalveolar carcinoma features in Japanese patients with adenocarcinoma. Jpn J Clin Oncol. 2006;36:69–75. 16. Lee HJ, Kim YT, Kang CH, et al. Epidermal growth factor receptor mutation in lung adenocarcinomas: relationship with CT characteristics and histologic subtypes. Radiology. 2013;268:254–264.
r
2014 Lippincott Williams & Wilkins
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17. Choi CM, Kim MY, Lee JC, et al. Advanced lung adenocarcinoma harboring a mutation of the epidermal growth factor receptor: CT findings after tyrosine kinase inhibitor therapy. Radiology. 2014;270:574–582. 18. Onn A, Choe DH, Herbst RS, et al. Tumor cavitation in stage I non-small cell lung cancer: epidermal growth factor receptor expression and prediction of poor outcome. Radiology. 2005; 237:342–347. 19. Jung CY. Biopsy and mutation detection strategies in nonsmall cell lung cancer. Tuberc Respir Dis (Seoul). 2013;75: 181–187. 20. Togashi Y, Masago K, Kubo T, et al. Association of diffuse, random pulmonary metastases, including miliary metastases, with epidermal growth factor receptor mutations in lung adenocarcinoma. Cancer. 2011;117:819–825. 21. Obenauer S, Hermann KP, Grabbe E. Applications and literature review of the BI-RADS classification. Eur Radiol. 2005;15:1027–1036. 22. Khan AN, Al-Jahdali HH, Allen CM, et al. The calcified lung nodule: what does it mean? Ann Thorac Med. 2010;5:67–79. 23. Jemal A, Bray F, Center MM, et al. Global cancer statistics. CA Cancer J Clin. 2011;61:69–90. 24. Travis WD, Travis LB, Devesa SS. Lung cancer. Cancer. 1995;75:191–202. 25. Auerbach O, Garfinkel L. The changing pattern of lung carcinoma. Cancer. 1991;68:1973–1977. 26. Lee CK, Brown C, Gralla RJ, et al. Impact of EGFR inhibitor in non-small cell lung cancer on progression-free and overall survival: a meta-analysis. J Natl Cancer Inst. 2013;105: 595–605. 27. Jackman DM, Yeap BY, Sequist LV, et al. Exon 19 deletion mutations of epidermal growth factor receptor are associated with prolonged survival in non-small cell lung cancer patients treated with gefitinib or erlotinib. Clin Cancer Res. 2006;12:3908–3914. 28. Zhu JQ, Zhong WZ, Zhang GC, et al. Better survival with EGFR exon 19 than exon 21 mutations in gefitinib-treated non-small cell lung cancer patients is due to differential inhibition of downstream signals. Cancer Lett. 2008;265: 307–317. 29. Hsieh RK, Lim KH, Kuo HT, et al. Female sex and bronchioloalveolar pathologic subtype predict EGFR mutations in non-small cell lung cancer. Chest. 2005;128: 317–321. 30. Jang TW, Oak CH, Chang HK, et al. EGFR and KRAS mutations in patients with adenocarcinoma of the lung. Korean J Intern Med. 2009;24:48–54. 31. Tsao AS, Tang XM, Sabloff B, et al. Clinicopathologic characteristics of the EGFR gene mutation in non-small cell lung cancer. J Thorac Oncol. 2006;1:231–239. 32. Travis WD, Brambilla E, Noguchi M, et al. International association for the study of lung cancer/american thoracic society/european respiratory society international multidisciplinary classification of lung adenocarcinoma. J Thorac Oncol. 2011;6:244–285. 33. Yanagawa M, Kuriyama K, Kunitomi Y, et al. One-dimensional quantitative evaluation of peripheral lung adenocarcinoma with or without ground-glass opacity on thin-section CT images using profile curves. Br J Radiol. 2009;82:532–540. 34. Aoki T, Hanamiya M, Uramoto H, et al. Adenocarcinomas with predominant ground-glass opacity: correlation of morphology and molecular biomarkers. Radiology. 2012;264: 590–596. 35. van ZN, Mathy A, Boerrigter L, et al. EGFR and KRAS mutations as criteria for treatment with tyrosine kinase inhibitors: retro- and prospective observations in non-smallcell lung cancer. Ann Oncol. 2007;18:99–103.
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