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Asia-Pacific Journal of Clinical Oncology 2015; 11: 28–33
doi: 10.1111/ajco.12195
ORIGINAL ARTICLE
Diagnostic value of soluble receptor-binding cancer antigen expressed on SiSo cells and carcinoembryonic antigen in malignant pleural effusion in patients with lung cancer Chun-hua XU,1 Ke-ke HAO,1 Li-ke YU1 and Xiu-wei ZHANG2 1 First Department of Respiratory Medicine, Nanjing Chest Hospital, and 2Department of Respiratory Medicine, Nanjing Jiangning Hospital, Nanjing, China
Abstract Aim: The aim of this study was to evaluate the diagnostic value of soluble receptor-binding cancer antigen expressed on SiSo cells (sRCAS1) and carcinoembryonic antigen (CEA) in lung cancer patients with malignant pleural effusion (MPE) and benign pleural effusion (BPE). Methods: Pleural effusion samples from 118 patients were classified on the basis of diagnosis as MPE (n = 60) and BPE (n = 58). The concentration of sRCAS1 was determined by enzyme-linked immunosorbent assay. The CEA levels were also determined in all patients. Results: Of 60 MPE patients, 50 had sRCAS1 > 9.7 U/mL and 54 had CEA > 5.5 ng/mL. The concentration of both sRCAS1 and CEA in MPE was significantly higher compared with that in BPE (P < 0.01 in both cases). With a cutoff point of 9.7 U/mL, sRCAS1 had a sensitivity of 83.3% and a specificity of 91.4% for differential diagnosis. The combined detection of sRCAS1 and CEA had a sensitivity of 98.3% and a specificity of 96.6% to distinguish MPE from BPE. Conclusion: The combined detection of sRCAS1 and CEA may be more valuable in the differential diagnosis between MPE and BPE. Key words: benign/malignant, lung cancer, pleural effusion, sRCAS1.
INTRODUCTION Malignant pleural effusion (MPE) is a common condition seen at the advanced stage of lung cancer. Approximately 30–40% of lung cancer patients develop pleural effusions later in their courses.1 The presence of MPE usually indicates the severity of illness and a short survival time.2 Differentiating malignant from benign pleural effusion (BPE) is a critical clinical problem, and
Correspondence: Professor Li-ke Yu PhD, First Department of Respiratory Medicine, Nanjing Chest Hospital, 215 Guangzhou Road, Nanjing 210029, China. Email: [email protected] Conflict of interest: none Accepted for publication 15 February 2014.
© 2014 Wiley Publishing Asia Pty Ltd
conventional methods have proven inadequate.3–6 Pleural fluid cytology has traditionally been the analytical method of choice for the detection of tumor cells in pleural fluid. However, sensitivity varies between 30 and 60%,7 and blindly obtained pleural needle biopsy specimens offer little additional sensitivity.8 Although the presence of tumor cells in pleural effusion is a diagnostic marker of MPE, the probability of finding them is low. For cytology-negative pleural effusion, some of the currently used indices, such as carcinoembryonic antigen (CEA), neuron-specific enolase and cytokeratin 19 fragments (CYFRA 21-1), have a certain extent of differential value; however, their specificity and sensitivity are limited.9,10 It is thus necessary to identify more reliable and easily used biomarkers that may enhance MPE diagnosis.11 Receptor-binding cancer antigen expressed on SiSo cells (RCAS1) is a type II membrane protein. RCAS1
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Diagnostic value of sRCAS1 and CEA in malignant pleural effusion
acts as a ligand for a putative receptor that is present in various human cell lines.12 In previous immunohistochemical studies, RCAS1 was expressed in various malignant tissues, including lung cancer.13,14 Soluble RCAS1 has been detected by enzyme-linked immunosorbent assay in a culture supernatant derived from a human bile duct carcinoma cell line.15 These findings suggest that sRCAS1 may serve as a tumor marker. We investigated the sRCAS1 levels in MPE and BPE to explore its value in the differential diagnosis between MPE and BPE.
present in pleural effusion or from biopsies specimen taken. Tuberculous pleural effusion was diagnosed according to the following principle: identification of acid-fast bacillus in pleural fluid, caseous granulomas in a pleural biopsy specimen, and a high level of pleural fluid adenosine deaminase (>40 U/L) with an improvement of the pleurisy after antituberculous therapy. Parapneumonic effusion was characterized by any pleural effusion associated with pneumonia and response to antibiotics. Patients with pleural empyema were also included in this group.
METHODS
Sample collection and determination of sRACS1 and CEA levels
Patients The study included 118 consecutive patients with pleural effusion who were recruited from the Nanjing Chest Hospital from January 2007 to December 2009. All pleural effusion had definite etiology documented by examination of effusion biochemistry, cytology, pleural biopsy, percutaneous biopsy, endoscopic examination and clinical follow-up. The characteristics of these patients are summarized in Table 1. This patient group included 63 men and 55 women with a mean age of 66 years; 60 patients (50.8%) had malignant effusions while 58 (49.2%) had benign effusions. The study protocol was approved by the Ethics Committee of Nanjing Chest Hospital. All patients provided written informed consent before enrollment.
Diagnostic criteria for pleural effusion The pleural effusions were firstly diagnosed as exudates using Light’s criteria. The diagnostic criteria for MPE are as follows: Cytological evidence of malignant cells
Table 1
Each sample of pleural fluid was collected in a syringe during a thoracentesis performed after written informed consent was obtained. Samples were centrifuged at 2000 rpm for 10 min, and the supernatant was frozen at −80°C until assayed. Soluble RACS1 levels were measured by sandwich enzyme-linked immunosorbent assay using commercially available kits (Medical and Biological Laboratories Co Ltd, Nanjing, China). The concentration of CEA was measured by electrochemiluminescence kits (Roche Diagnostics, Beijing, China). All assays were run in duplicate, with dilutions as appropriate, and the technicians were blinded to clinical data.
Statistical analysis Statistical analysis was carried out using SPSS 17.0 software. Differences between independent groups were examined by the Mann–Whitney U-test. Significance testing of correlations was evaluated using Spearman’s rank correlation analysis. Receiver operating curve
Patient characteristics
Variables Subject, NO Age, year Male/female MPE Adenocarcinoma Squamous cell carcinoma Small cell lung carcinoma BPE Tuberculosis Parapneumonic
Asia-Pac J Clin Oncol 2015; 11: 28–33
MPE
BPE
P-value
60 54.3 ± 11.7 33/27
58 53.5 ± 12.8 30/28
>0.05 >0.05
50 4 6
ND ND ND
ND ND ND
48 10
ND ND
ND ND
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(ROC) analysis was used to evaluate the threshold value of sRACS1 and CEA in differentiating MPE from BPE. For each ROC, a cutoff point was determined as the value of the parameter that maximized the sum of specificity and sensitivity. A value of P < 0.05 was considered significant.
RESULTS The concentration of CEA and sRACS1 in pleural effusion As shown in Figure 1a, the concentration of sRCAS1 was significantly higher in patients with MPE (19.2 ± 6.1 U/mL) than in those with BPE (6.7 ± 3.6 U/mL) (P < 0.01). Figure 1b showed that the level of CEA was 31.7 ± 14.5 ng/mL in MPE, and it was significantly higher compared with the value of 4.1 ± 2.4 ng/mL found in BPE (P < 0.01).
Diagnostic value of sRCAS1 in MPE and BPE The diagnostic threshold afforded by the ROC analysis for sRCAS1 was 9.7 U/mL (Fig. 2a). The area under the sRCAS1 ROC was 0.905. Using a cutoff point of 9.7 U/ mL, sRCAS1 had a sensitivity of 83.3% (50/60), a specificity of 91.4% (53/58), an accuracy of 87.3% (103/
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118), a positive predictive value (PPV) of 90.9% (50/55) and a negative predictive value (NPV) of 84.1% (53/63) (Table 2).
Diagnostic value of combined detection of sRCAS1 and CEA in MPE and BPE Firstly, CEA levels were detected and the diagnostic value in MPE and BPE was analyzed. The diagnostic threshold afforded by the ROC analysis for CEA was 5.5 ng/mL. The area under the CEA ROC was 0.927. It was higher compared with the areas of sRCAS1 (Fig. 2b). With a cutoff point of 5.5 ng/mL, CEA had a sensitivity of 90.0% (54/60), a specificity of 91.4% (53/ 58), an accuracy of 90.7% (107/118), a PPV of 91.5% (54/59) and a NPV of 89.8% (53/59) (Table 2). The sensitivity of sRCAS1 was lower compared with CEA. Between the studied parameters, sRCAS1 and CEA, no significant differences were found with respect to the specificity. The combined diagnostic value of sRCAS1 and CEA in MPE and BPE was further detected. The results showed that the combined detection of these two indices had a sensitivity of 98.3% (59/60) and a specificity of 96.6% (56/58) (Table 2). The combination of sRCAS1 and CEA produced better sensitivity and specificity than sRCAS1 and CEA alone (Fig. 2c).
Figure 1 Levels of sRCAS1 and carcinoembryonic antigen (CEA) in pleural effusion between benign and malignant groups. (a) sRCAS1. (b) CEA. *P < 0.01 compared with benign pleural effusion (BPE) group.
© 2014 Wiley Publishing Asia Pty Ltd
Asia-Pac J Clin Oncol 2015; 11: 28–33
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Diagnostic value of sRCAS1 and CEA in malignant pleural effusion
Figure 2 Receiver operating curve (ROC) in pleural effusion. (a) sRCAS1 ROC; (b) CEA ROC; (c) sRCAS1 + CEA ROC. The areas under the curve of pleural effusion sRCAS1, CEA and sRCAS1 + CEA were 0.905, 0.927 and 0.943, respectively. CEA, carcinoembryonic antigen.
Table 2
Diagnostic values of sRCAS1 and CEA for predicting MPE
Variables sRCAS1 CEA sRCAS1 + CEA
Sensitivity (%)
Specificity (%)
Accuracy (%)
PPV (%)
NPV (%)
83.3 (50/60) 90.0 (54/60) 98.3 (59/60)
91.4 (53/58) 91.4 (53/58) 96.6 (56/58)
87.3 (103/118) 90.7 (107/118) 97.5 (115/118)
90.9 (50/55) 91.5 (54/59) 96.7 (59/61)
84.1 (53/63) 89.8 (53/59) 98.2 (56/57)
Correlation between sRCAS1 and CEA in MPE As shown in Figure 3, there is a significant correlation between sRCAS1 and CEA levels in MPE (r = 0.292, P = 0.024).
DISCUSSION In the present study, we show that the concentration of sRCAS1 is higher in MPE than in BPE. The level of CEA was also significantly higher in MPE. Furthermore, when using the combined detection of sRCAS1 and CEA, the diagnostic value was more accurate compared with the single index. Cytotoxic T lymphocytes recognizing tumor-specific antigens and nature killer (NK) cells are important in tumor elimination at early stages of cancer progression or metastasis. Because RCAS1-receptor expression is upregulated by activation of lymphocytes, RCAS1 helps
Asia-Pac J Clin Oncol 2015; 11: 28–33
induce cell arrest and apoptosis by activating NK and T cells. These findings indicate that RCAS1 on tumor cells may convey an important advantage in avoiding host immune surveillance. RCAS1 is expressed in various cancers including those of the lung,13,14 esophagus,16 breast,17 liver,18 pancreas,19 stomach20,21 and gallbladder.22 RCAS1 expression has also been associated with aggressive tumor phenotypes, such as poor differentiation and advanced stage.19,20 Furthermore, RCAS1 expression was reported to be significantly and negatively related to overall survival of patients with cancers of the lung,13,14 esophagus16 and stomach.20 Thus, the concentration of RCAS1 may indicate the aggressiveness of tumors behavior in humans. However, the diagnostic value of sRCAS1 in MPE remains few. Aoe et al. reported that the sRCAS1 concentrations in malignant pleural fluid were higher than those in nonmalignant pleural fluid.23,24 In this study, the sRCAS1 concentration in MPE was higher than that in BPE (P < 0.01). Our results suggest
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Figure 3 Correlation of pleural effusion sRCAS1 concentration with carcinoembryonic antigen (CEA).
that sRCAS1 should be an informative tumor marker for the diagnosis of MPE. The diagnostic value of sRCAS1 in MPE was 9.7 U/mL and had a sensitivity of 83.3% and a specificity of 91.4%. This shows that the sRCAS1 is a valuable parameter in the differential diagnosis of MPE and BPE. In addition, we found that there is a significant correlation between sRCAS1 and CEA, potential markers in pleural fluid that have shown limited reliability when considered separately.24 Thus, our results suggest a role for sRCAS1 in a panel of diagnostic markers for MPE. CEA has been found to have a differential value in distinguishing MPE from BPE.25 In our study, the diagnostic value of CEA in MPE and BPE was 5.5 ng/mL. The threshold value of the diagnosis of MPE and BPE had a sensitivity of 90.0% and a specificity of 91.4%. These results are consistent with those from the study by Shi et al.26 The combined diagnostic value of the sRCAS1 and CEA in MPE and BPE was further analyzed. The results showed that the combined detection of these two indices had a sensitivity of 98.3% and a specificity of 96.6%. The sensitivity and specificity were higher compared with the separate tests for MPE and BPE. This shows that the combined use of sRCAS1 and CEA had a better diagnostic value than the use of a single index. This may provide a new approach in the differential diagnosis of MPE and BPE. In summary, our results suggest that sRCAS1 is higher in MPE compared with BPE. The combined detection of
© 2014 Wiley Publishing Asia Pty Ltd
CEA and sRCAS1 had a higher sensitivity and specificity compared with the single index. This may effectively improve the diagnostic performance.
REFERENCES 1 Cheng D, Liang B, Li YH. Application of MMP-7 and MMP-10 in assisting the diagnosis of malignant pleural effusion. Asian Pac J Cancer Prev 2012; 13: 505–9. 2 Postmus PE, Brambilla E, Chansky K et al. The IASLC Lung Cancer Staging Project: proposals for revision of the M descriptors in the forthcoming (seventh) edition of the TNM classification of lung cancer. J Thorac Oncol 2007; 2: 686–93. 3 Aoe K, Hiraki A, Murakami T et al. Diagnostic significance of interferon-gamma in tuberculous pleural effusions. Chest 2003; 123: 740–4. 4 Aoe K, Hiraki A, Murakami T et al. Relative abundance and patterns of correlation among six cytokines in pleural fluid measured by cytometric bead array. Int J Mol Med 2003; 12: 193–8. 5 Hiraki A, Aoe K, Matsuo K et al. Simultaneous measurement of T-helper 1 cytokines in tuberculous pleural effusion. Int J Tuberc Lung Dis 2003; 7: 1172–7. 6 Hiraki A, Aoe K, Eda R et al. Comparison of six biological markers for the diagnosis of tuberculous pleuritis. Chest 2004; 125: 987–9. 7 Sriram KB, Relan V, Clarke BE et al. Diagnostic molecular biomarkers for malignant pleural effusions. Future Oncol 2011; 7: 737–52. 8 Heffner JE. Diagnosis and management of malignant pleural effusions. Respirology 2008; 13: 5–20.
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Diagnostic value of sRCAS1 and CEA in malignant pleural effusion
9 Villena V, López-Encuentra A, Echave-Sustaeta J et al. Diagnostic value of CA 549 in pleural fluid. Comparison with CEA, CA 15.3 and CA 72.4. Lung Cancer 2003; 40: 289–94. 10 Porcel JM, Vives M, Esquerda A et al. Use of a panel of tumor markers (carcinoembryonic antigen, cancer antigen 125, carbohydrate antigen 15-3, and cytokeratin 19 fragments) in pleural fluid for the differential diagnosis of benign and malignant effusions. Chest 2004; 126: 1757– 63. 11 Liang QL, Shi HZ, Qin XJ et al. Diagnostic accuracy of tumour markers for malignant pleural effusion: a metaanalysis. Thorax 2008; 63: 35–41. 12 Nakashima T, Sonoda K, Watanabe T. Inhibition of cell growth and induction of apoptotic cell death by the human tumor-associated antigen RCAS1. Nat Med 1999; 5: 938– 42. 13 Izumi M, Nakanishi Y, Yoshino I et al. Expression of tumor-associated antigen RCAS1 correlates significantly with poor prognosis in non-small cell lung carcinoma. Cancer 2001; 92: 446–51. 14 Oizumi S, Yamazaki K, Nakashima M et al. RCAS1 expression: a potential prognostic marker for adenocarcinoma of the lung. Oncology 2002; 62: 333–9. 15 Enjoji M, Nakashima M, Nishi H et al. The tumorassociated antigen, RCAS1, can be expressed in immunemediated disease as well as in carcinomas of biliary tract. J Hepatol 2002; 36: 786–92. 16 Coban S, Ozkan H, Köklü S et al. The utility of serum receptor-binding cancer antigen expressed on SiSo cells in gastrointestinal tract cancers. Can J Gastroenterol 2006; 20: 593–6. 17 Popiela TJ, Rudnicka-Sosin L, Dutsch-Wicherek M et al. The metallothionein and RCAS1 expression analysis in breast cancer and adjacent tissue regarding the immune
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cells presence and their activity. Neuro Endocrinol Lett 2006; 27: 786–94. Enjoji M, Nakashima M, Yamaguchi K et al. Significance of RCAS1 antigen in hepatocellular, cholangiocellular and pancreatic carcinomas. J Gastroenterol Hepatol 2005; 20: 1143–8. Ozkan H, Akar T, Köklü S, Coban S. Significance of serum receptor-binding cancer antigen (RCAS1) in pancreatic cancer and benign pancreatobiliary diseases. Pancreatology 2006; 6: 268–72. Kubokawa M, Nakashima M, Yao T et al. Aberrant intracellular localization of RCAS1 is associated with tumor progression of gastric cancer. Int J Oncol 2001; 19: 695– 700. Nakamura Y, Yamazaki K, Oizumi S et al. Expression of RCAS1 in human gastric carcinoma: a potential mechanism of immune escape. Cancer Sci 2004; 95: 260–5. Rupesh P, Manoj P, Vijay Kumar S. Biomarkers in carcinoma of the gallbladder. Expert Opin Med Diagn 2008; 2: 511–26. Aoe K, Hiraki A, Maeda T et al. Soluble receptor-binding cancer antigen expressed on SiSo cells in pleural fluid: a potential diagnostic marker for malignant pleural effusion. Chest 2004; 126: 1195–7. Aoe K, Hiraki A, Yamazaki K et al. Elevated pleural fluid RCAS1 is a diagnostic marker and outcome predictor in lung cancer patients. Int J Oncol 2006; 29: 65–72. Korczynski P, Krenme R, Saflanowska A et al. Diagnostic utility of pleural fluid and serum markers in differentiation between malignant and non-malignant pleural effusions. Eur J Med Res 2009; 4: 128–33. Shi HZ, Liang QL, Jiang J et al. Diagnostic value of carcinoembryonic antigen in malignant pleural effusion a meta-analysis. Respirology 2008; 13: 518–27.
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Asia-Pacific Journal of Clinical Oncology 2015; 11: 28–33
doi: 10.1111/ajco.12195
ORIGINAL ARTICLE
Diagnostic value of soluble receptor-binding cancer antigen expressed on SiSo cells and carcinoembryonic antigen in malignant pleural effusion in patients with lung cancer Chun-hua XU,1 Ke-ke HAO,1 Li-ke YU1 and Xiu-wei ZHANG2 1 First Department of Respiratory Medicine, Nanjing Chest Hospital, and 2Department of Respiratory Medicine, Nanjing Jiangning Hospital, Nanjing, China
Abstract Aim: The aim of this study was to evaluate the diagnostic value of soluble receptor-binding cancer antigen expressed on SiSo cells (sRCAS1) and carcinoembryonic antigen (CEA) in lung cancer patients with malignant pleural effusion (MPE) and benign pleural effusion (BPE). Methods: Pleural effusion samples from 118 patients were classified on the basis of diagnosis as MPE (n = 60) and BPE (n = 58). The concentration of sRCAS1 was determined by enzyme-linked immunosorbent assay. The CEA levels were also determined in all patients. Results: Of 60 MPE patients, 50 had sRCAS1 > 9.7 U/mL and 54 had CEA > 5.5 ng/mL. The concentration of both sRCAS1 and CEA in MPE was significantly higher compared with that in BPE (P < 0.01 in both cases). With a cutoff point of 9.7 U/mL, sRCAS1 had a sensitivity of 83.3% and a specificity of 91.4% for differential diagnosis. The combined detection of sRCAS1 and CEA had a sensitivity of 98.3% and a specificity of 96.6% to distinguish MPE from BPE. Conclusion: The combined detection of sRCAS1 and CEA may be more valuable in the differential diagnosis between MPE and BPE. Key words: benign/malignant, lung cancer, pleural effusion, sRCAS1.
INTRODUCTION Malignant pleural effusion (MPE) is a common condition seen at the advanced stage of lung cancer. Approximately 30–40% of lung cancer patients develop pleural effusions later in their courses.1 The presence of MPE usually indicates the severity of illness and a short survival time.2 Differentiating malignant from benign pleural effusion (BPE) is a critical clinical problem, and
Correspondence: Professor Li-ke Yu PhD, First Department of Respiratory Medicine, Nanjing Chest Hospital, 215 Guangzhou Road, Nanjing 210029, China. Email: [email protected] Conflict of interest: none Accepted for publication 15 February 2014.
© 2014 Wiley Publishing Asia Pty Ltd
conventional methods have proven inadequate.3–6 Pleural fluid cytology has traditionally been the analytical method of choice for the detection of tumor cells in pleural fluid. However, sensitivity varies between 30 and 60%,7 and blindly obtained pleural needle biopsy specimens offer little additional sensitivity.8 Although the presence of tumor cells in pleural effusion is a diagnostic marker of MPE, the probability of finding them is low. For cytology-negative pleural effusion, some of the currently used indices, such as carcinoembryonic antigen (CEA), neuron-specific enolase and cytokeratin 19 fragments (CYFRA 21-1), have a certain extent of differential value; however, their specificity and sensitivity are limited.9,10 It is thus necessary to identify more reliable and easily used biomarkers that may enhance MPE diagnosis.11 Receptor-binding cancer antigen expressed on SiSo cells (RCAS1) is a type II membrane protein. RCAS1
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Diagnostic value of sRCAS1 and CEA in malignant pleural effusion
acts as a ligand for a putative receptor that is present in various human cell lines.12 In previous immunohistochemical studies, RCAS1 was expressed in various malignant tissues, including lung cancer.13,14 Soluble RCAS1 has been detected by enzyme-linked immunosorbent assay in a culture supernatant derived from a human bile duct carcinoma cell line.15 These findings suggest that sRCAS1 may serve as a tumor marker. We investigated the sRCAS1 levels in MPE and BPE to explore its value in the differential diagnosis between MPE and BPE.
present in pleural effusion or from biopsies specimen taken. Tuberculous pleural effusion was diagnosed according to the following principle: identification of acid-fast bacillus in pleural fluid, caseous granulomas in a pleural biopsy specimen, and a high level of pleural fluid adenosine deaminase (>40 U/L) with an improvement of the pleurisy after antituberculous therapy. Parapneumonic effusion was characterized by any pleural effusion associated with pneumonia and response to antibiotics. Patients with pleural empyema were also included in this group.
METHODS
Sample collection and determination of sRACS1 and CEA levels
Patients The study included 118 consecutive patients with pleural effusion who were recruited from the Nanjing Chest Hospital from January 2007 to December 2009. All pleural effusion had definite etiology documented by examination of effusion biochemistry, cytology, pleural biopsy, percutaneous biopsy, endoscopic examination and clinical follow-up. The characteristics of these patients are summarized in Table 1. This patient group included 63 men and 55 women with a mean age of 66 years; 60 patients (50.8%) had malignant effusions while 58 (49.2%) had benign effusions. The study protocol was approved by the Ethics Committee of Nanjing Chest Hospital. All patients provided written informed consent before enrollment.
Diagnostic criteria for pleural effusion The pleural effusions were firstly diagnosed as exudates using Light’s criteria. The diagnostic criteria for MPE are as follows: Cytological evidence of malignant cells
Table 1
Each sample of pleural fluid was collected in a syringe during a thoracentesis performed after written informed consent was obtained. Samples were centrifuged at 2000 rpm for 10 min, and the supernatant was frozen at −80°C until assayed. Soluble RACS1 levels were measured by sandwich enzyme-linked immunosorbent assay using commercially available kits (Medical and Biological Laboratories Co Ltd, Nanjing, China). The concentration of CEA was measured by electrochemiluminescence kits (Roche Diagnostics, Beijing, China). All assays were run in duplicate, with dilutions as appropriate, and the technicians were blinded to clinical data.
Statistical analysis Statistical analysis was carried out using SPSS 17.0 software. Differences between independent groups were examined by the Mann–Whitney U-test. Significance testing of correlations was evaluated using Spearman’s rank correlation analysis. Receiver operating curve
Patient characteristics
Variables Subject, NO Age, year Male/female MPE Adenocarcinoma Squamous cell carcinoma Small cell lung carcinoma BPE Tuberculosis Parapneumonic
Asia-Pac J Clin Oncol 2015; 11: 28–33
MPE
BPE
P-value
60 54.3 ± 11.7 33/27
58 53.5 ± 12.8 30/28
>0.05 >0.05
50 4 6
ND ND ND
ND ND ND
48 10
ND ND
ND ND
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(ROC) analysis was used to evaluate the threshold value of sRACS1 and CEA in differentiating MPE from BPE. For each ROC, a cutoff point was determined as the value of the parameter that maximized the sum of specificity and sensitivity. A value of P < 0.05 was considered significant.
RESULTS The concentration of CEA and sRACS1 in pleural effusion As shown in Figure 1a, the concentration of sRCAS1 was significantly higher in patients with MPE (19.2 ± 6.1 U/mL) than in those with BPE (6.7 ± 3.6 U/mL) (P < 0.01). Figure 1b showed that the level of CEA was 31.7 ± 14.5 ng/mL in MPE, and it was significantly higher compared with the value of 4.1 ± 2.4 ng/mL found in BPE (P < 0.01).
Diagnostic value of sRCAS1 in MPE and BPE The diagnostic threshold afforded by the ROC analysis for sRCAS1 was 9.7 U/mL (Fig. 2a). The area under the sRCAS1 ROC was 0.905. Using a cutoff point of 9.7 U/ mL, sRCAS1 had a sensitivity of 83.3% (50/60), a specificity of 91.4% (53/58), an accuracy of 87.3% (103/
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118), a positive predictive value (PPV) of 90.9% (50/55) and a negative predictive value (NPV) of 84.1% (53/63) (Table 2).
Diagnostic value of combined detection of sRCAS1 and CEA in MPE and BPE Firstly, CEA levels were detected and the diagnostic value in MPE and BPE was analyzed. The diagnostic threshold afforded by the ROC analysis for CEA was 5.5 ng/mL. The area under the CEA ROC was 0.927. It was higher compared with the areas of sRCAS1 (Fig. 2b). With a cutoff point of 5.5 ng/mL, CEA had a sensitivity of 90.0% (54/60), a specificity of 91.4% (53/ 58), an accuracy of 90.7% (107/118), a PPV of 91.5% (54/59) and a NPV of 89.8% (53/59) (Table 2). The sensitivity of sRCAS1 was lower compared with CEA. Between the studied parameters, sRCAS1 and CEA, no significant differences were found with respect to the specificity. The combined diagnostic value of sRCAS1 and CEA in MPE and BPE was further detected. The results showed that the combined detection of these two indices had a sensitivity of 98.3% (59/60) and a specificity of 96.6% (56/58) (Table 2). The combination of sRCAS1 and CEA produced better sensitivity and specificity than sRCAS1 and CEA alone (Fig. 2c).
Figure 1 Levels of sRCAS1 and carcinoembryonic antigen (CEA) in pleural effusion between benign and malignant groups. (a) sRCAS1. (b) CEA. *P < 0.01 compared with benign pleural effusion (BPE) group.
© 2014 Wiley Publishing Asia Pty Ltd
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Diagnostic value of sRCAS1 and CEA in malignant pleural effusion
Figure 2 Receiver operating curve (ROC) in pleural effusion. (a) sRCAS1 ROC; (b) CEA ROC; (c) sRCAS1 + CEA ROC. The areas under the curve of pleural effusion sRCAS1, CEA and sRCAS1 + CEA were 0.905, 0.927 and 0.943, respectively. CEA, carcinoembryonic antigen.
Table 2
Diagnostic values of sRCAS1 and CEA for predicting MPE
Variables sRCAS1 CEA sRCAS1 + CEA
Sensitivity (%)
Specificity (%)
Accuracy (%)
PPV (%)
NPV (%)
83.3 (50/60) 90.0 (54/60) 98.3 (59/60)
91.4 (53/58) 91.4 (53/58) 96.6 (56/58)
87.3 (103/118) 90.7 (107/118) 97.5 (115/118)
90.9 (50/55) 91.5 (54/59) 96.7 (59/61)
84.1 (53/63) 89.8 (53/59) 98.2 (56/57)
Correlation between sRCAS1 and CEA in MPE As shown in Figure 3, there is a significant correlation between sRCAS1 and CEA levels in MPE (r = 0.292, P = 0.024).
DISCUSSION In the present study, we show that the concentration of sRCAS1 is higher in MPE than in BPE. The level of CEA was also significantly higher in MPE. Furthermore, when using the combined detection of sRCAS1 and CEA, the diagnostic value was more accurate compared with the single index. Cytotoxic T lymphocytes recognizing tumor-specific antigens and nature killer (NK) cells are important in tumor elimination at early stages of cancer progression or metastasis. Because RCAS1-receptor expression is upregulated by activation of lymphocytes, RCAS1 helps
Asia-Pac J Clin Oncol 2015; 11: 28–33
induce cell arrest and apoptosis by activating NK and T cells. These findings indicate that RCAS1 on tumor cells may convey an important advantage in avoiding host immune surveillance. RCAS1 is expressed in various cancers including those of the lung,13,14 esophagus,16 breast,17 liver,18 pancreas,19 stomach20,21 and gallbladder.22 RCAS1 expression has also been associated with aggressive tumor phenotypes, such as poor differentiation and advanced stage.19,20 Furthermore, RCAS1 expression was reported to be significantly and negatively related to overall survival of patients with cancers of the lung,13,14 esophagus16 and stomach.20 Thus, the concentration of RCAS1 may indicate the aggressiveness of tumors behavior in humans. However, the diagnostic value of sRCAS1 in MPE remains few. Aoe et al. reported that the sRCAS1 concentrations in malignant pleural fluid were higher than those in nonmalignant pleural fluid.23,24 In this study, the sRCAS1 concentration in MPE was higher than that in BPE (P < 0.01). Our results suggest
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C Xu et al.
Figure 3 Correlation of pleural effusion sRCAS1 concentration with carcinoembryonic antigen (CEA).
that sRCAS1 should be an informative tumor marker for the diagnosis of MPE. The diagnostic value of sRCAS1 in MPE was 9.7 U/mL and had a sensitivity of 83.3% and a specificity of 91.4%. This shows that the sRCAS1 is a valuable parameter in the differential diagnosis of MPE and BPE. In addition, we found that there is a significant correlation between sRCAS1 and CEA, potential markers in pleural fluid that have shown limited reliability when considered separately.24 Thus, our results suggest a role for sRCAS1 in a panel of diagnostic markers for MPE. CEA has been found to have a differential value in distinguishing MPE from BPE.25 In our study, the diagnostic value of CEA in MPE and BPE was 5.5 ng/mL. The threshold value of the diagnosis of MPE and BPE had a sensitivity of 90.0% and a specificity of 91.4%. These results are consistent with those from the study by Shi et al.26 The combined diagnostic value of the sRCAS1 and CEA in MPE and BPE was further analyzed. The results showed that the combined detection of these two indices had a sensitivity of 98.3% and a specificity of 96.6%. The sensitivity and specificity were higher compared with the separate tests for MPE and BPE. This shows that the combined use of sRCAS1 and CEA had a better diagnostic value than the use of a single index. This may provide a new approach in the differential diagnosis of MPE and BPE. In summary, our results suggest that sRCAS1 is higher in MPE compared with BPE. The combined detection of
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CEA and sRCAS1 had a higher sensitivity and specificity compared with the single index. This may effectively improve the diagnostic performance.
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