Acta Neurol Scand 2015: 132: 310–322 DOI: 10.1111/ane.12401
© 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd ACTA NEUROLOGICA SCANDINAVICA
Prognostic value of epidermal growth factor receptor amplification and EGFRvIII in glioblastoma: meta-analysis Chen J-R, Xu H-Z, Yao Y, Qin Z-Y. Prognostic value of epidermal growth factor receptor amplification and EGFRvIII in glioblastoma: meta-analysis. Acta Neurol Scand 2015: 132: 310–322. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd. Objectives – Epidermal growth factor receptor (EGFR) gene amplification and the EGFRvIII mutation may have prognostic value in patients with glioblastoma. This meta-analysis was to determine whether EGFR gene amplification or the EGFRvIII mutation are predictors of survival in patients with glioblastoma and anaplastic astrocytoma. Materials and methods – Medline, the Cochrane Central Register of Controlled Trials, EMBASE, and Google Scholar databases were searched until July 31, 2014. Studies were selected for inclusion in the analysis if they included patients with anaplastic astrocytoma and/or glioblastoma, EGFR and/or EGFRvIII mutation status was reported, and overall survival (OS) data were reported. Results – Of 113 articles initially identified, only eight contained data with respect to the outcome of interest and were included in the metaanalysis. The number of cases ranged from 14 to 268, and the majority of patients were 60 or more years of age. There was no significant difference in OS between EGFR amplification-positive and EGFR amplification-negative glioblastoma patients (pooled hazard ratio [HR] = 1.101, 95% confidence interval [CI] 0.845, 1.434, P = 0.475) or anaplastic astrocytoma patients (pooled HR = 1.455, 95% CI 0.852, 2.482, P = 0.169). There was no significant difference in OS between EGFRvIII-positive and EGFRvIII-negative glioblastoma patients (pooled HR = 1.321, 95% CI: 0.881–1.981, P = 0.178). Significant heterogeneity existed between the studies, and the significance changed when the analysis was performed with studies removed in turn. Conclusions – There is insufficient evidence that either EGFR amplification or the EGFRvIII mutation has prognostic value in patients with glioblastoma.
Introduction
Glioblastoma multiforme (GBM) is the most common malignant primary brain tumor and has an annual incidence of approximately three cases per 100,000 persons (1, 2). Anaplastic astrocytomas (World Health Organization grade III) account for approximately 10% of all gliomas and exhibit a variable biological behavior (3, 4). Most centers believe that maximal safe resection for eligible patients followed by fractionated radiation therapy and temazolamide represent the 310
J.-R. Chen, H.-Z. Xu, Y. Yao, Z.-Y. Qin Department of Neurosurgery, Huashan Hospital Shanghai Medical College, Fudan University, Shanghai, China
Key words: epidermal growth factor; receptor; epidermal growth factor receptor VIII; glioblastoma; prognosis; survival analysis Z.-Y. Qin, No 12, Middle Wulumuqi Road, Shanghai 200040, China Tel.: +86-21-38719999-2097 Fax: 86-21-50309919 e-mail: [email protected] Accepted for publication March 4, 2015
current standard of care for GBM (5, 6). The prognosis, however, is poor with an overall survival (OS) of 10–12 months (5, 7). For patients with anaplastic astrocytomas, the overall agestandardized 5- and 10-year relative survival rates are 23.6% and 15.1%, respectively (8). The most frequent genetic alteration associated with GBM is amplification of the epidermal growth factor receptor (EGFR) gene (9). Amplification results in overexpression of EGFR, a transmembrane tyrosine kinase receptor. The majority of GBMs with EGFR amplification also
EGFR and glioblastoma prognosis contain EGFRvIII, a mutant EGFR gene that is characterized by the deletion of exons 2 to 7 (9). EGFR is overexpressed in approximately 50–60% of GBMs, and EGFRvIII is found in 24–67% of cases (9, 10). Study of EGFR variations is important as tyrosine kinase inhibitors have shown promise in the treatment of GBM (11). Evidence that EGFR amplification is an independent predictor of survival in patients with GBM varies considerably between studies (1, 10, 12–18). In a previous study, EGFR amplification was not found to be a significant prognostic indicator of OS or radiographic local control in GBM patients treated with surgery (19). On the other hand, Shinojima et al. (20) reported that EGFR amplification was an independent and significant predictor of poorer OS. Other reports have indicated that EGFRvIII overexpression in the presence of EGFR amplification is the strongest indicator of poor survival (16). Contrarily, Bie nkowski et al. (14) reported that EGFRvIII expression was associated with a better prognosis. Other study has suggested that EGFRvIII status defines clinically distinct GBM subsets (21). Thus, the aim of this meta-analysis was to determine whether EGFR gene amplification or the EGFRvIII mutation is an independent predictor of survival in patients with GBM and anaplastic astrocytoma. Materials and methods Search strategy
This systematic review and meta-analysis was conducted in accordance with PRISMA guidelines (22). Medline, the Cochrane Central Register of Controlled Trials, EMBASE, and Google Scholar databases were searched until July 31, 2014 using combinations of the following terms: glioma, GBM, anaplastic astrocytoma, prognostic, prognosis, survival, EGFR, and EGFRvIII mutation. Reference lists of relevant studies were hand-searched. Selection criteria
Studies were selected for inclusion in the analysis if they included patients with anaplastic astrocytoma and/or GBM, EGFR and/or EGFRvIII mutation status was reported, and OS data were reported. Studies in which patients had primary glioma or other types of brain tumors, non-English publications, proceedings, personal communications, letters, comments,
editorials, and case reports were excluded. Studies were identified by the search strategy by two independent reviewers. When there was uncertainty regarding eligibility, a third reviewer was consulted. Data extraction
Data extraction was performed by two independent reviewers, and a third reviewer was consulted for any uncertainties. The following information was extracted from studies that met the inclusion criteria: the name of the first author, year of publication, study design, patient type/disease status, KPS, EGFR amplification and EGFRvIII mutation status, treatment, length of follow-up, and survival outcomes. Quality assessment
The modified 18-item Delphi checklist was used to assess the quality of the included studies (23). Quality assessment was performed by the independent reviewers, and a third reviewer was consulted for any uncertainties. Outcome measures and data analysis
The outcome measure was OS. Hazard ratios (HRs) with 95% confidence intervals (CIs) were calculated for OS in patients who were EGFR amplification positive or EGFRvIII positive compared to patients who were EGFR amplification negative or EGFRvIII negative, respectively. For OS, a HR > 1 indicates the HR is associated with worse survival. Heterogeneity among the studies was assessed by the Cochran Q and the I2 statistic. For Cochran Q, a value of P < 0.10 was considered to indicate statistically significant heterogeneity. For the I2 statistic, no heterogeneity was indicated when I2 = 0–25%, moderate heterogeneity when I2 = 25–50%, large heterogeneity when I2 = 50–75%, and extreme heterogeneity when I2 = 75–100%. A fixed-effects model of analysis was used for this study because of the small number of articles for each outcome (24). Sensitivity analysis using the leave-one-out approach was performed to examine the influence of individual studies on pooled estimates. Pooled HRs were calculated, and a two-sided P-value < 0.05 was considered to indicate statistical significance. All statistical analyses were performed using Comprehensive Meta-Analysis version 2.0 software (Biostat, Englewood, NJ, USA). 311
314 17.90 NA NA NA NA NA NA NA NA 6 NA NA 46 23 NA NA NA NA NA 71 NA
12.30 NA NA NA NA NA NA NA NA 10 NA NA 67 6 NA NA
NA NA NA 43 NA
+
Survival rate (%)
NA NA 19.2 6.9 22.1
13.4 (9.7, 17.0) NA 4.73 NA NA NA 504 days 12 10.5 11.1 NA NA 13.2 14.4 666 days 8
+
HR (95% CI), + vs
NA NA 33.6 34.1 22.9
11.0 (9.5, 12.6) NA 4.8 NA NA NA 458 days 12 2 9.4 NA NA 10.7 20.16 284 days 11 0.69 (0.23, 2.11) 1.24 (0.50, 3.08) 2.5 (1.1, 5.7) NA NA
NA 1.279 NA 0.92 (0.67, 1.27) 1.07 (0.17, 6.89) NA 0.69 NA NA NA 0.39 (0.46–1.40) * 0.881 NA 1.67 (1.03–2.72) NA NA NA NA NA 22 NA
8.80 NA NA NA NA 5% NA NA NA NA NA NA 59 NA NA NA
+
NA NA NA 72 NA
16.90 NA NA NA NA 21% NA NA NA NA NA NA 54 NA NA NA NA NA NA 7.2 NA
11.6 (10.6, 12.5) NA 3.27 NA NA NA NA NA NA NA NA NA 12.4 11.6 NA NA
+
NA NA NA 33 NA
11.9 (10.2, 13.6) NA 4.93 NA NA NA NA NA NA NA NA NA 12.6 16.7 NA NA
Median survival time, months (95% CI)
Median survival time, months (95% CI) Survival rate (%)
OS – EGFRvIII
OS – EGFR amplification
CI, confidence interval; HR, hazard ratio; NA, not available; OS, overall survival. Note, + and refer to EGFR amplification positive and EGFR amplification negative, or EGFRvIII positive or EGFRvIII negative. *Median (range).
Glioblastoma Weller (2014) Bienkowski (2013) Lv (2012) Srividya (2010) Viana-Pereira (2008) Pelloski (2007) Houillier (2006) Layfield (2006) Kleinschmidt-DeMasters (2005) Quan (2005) Shih (2005) Batchelor (2004) Aldape (2004) Shinojima (2003) Hurtt (1992) Torp (1992) Anaplastic astrocytoma Gulati (2010) Kouwenhoven (2009) Idbaih (2008) Aldape (2004) Smith (2001)
First author (year of publication)
Table 2 Summary of study outcomes
NA NA NA NA NA
0.75 (0.44, 1.29) 0.337 NA NA 0.73 (0.13, 4.09) 3.37 (1.74, 6.50) NA NA NA NA NA NA NA NA NA NA
HR (95% CI), + vs
Chen et al.
EGFR and glioblastoma prognosis Table 1 Summary of the studies included in the meta-analysis First author (year of publication)
Number of cases
KPS/WHO performance score
Age (years)
Male (%)
Cohort
184
Cohort Prospective phase II trial Cohort Cohort NA
83 35 140 55 268
Houillier (2006) Layfield (2006)
Cohort Retrospective
220 32
>60: 55% ≤60: 45% 60 (23, 84)* 54 (33, 73)* 47 (18, 65)* 56.1 (27, 79)† 40: 40% 40–60: 36% >60: 24%
54
62
56
KPS, Karnofsky performance status; NA, not available; RCT, randomized controlled trial; WHO, World Health Organization. *Median (range). † Mean (range).
significant different in OS between the EGFR amplification-positive and EGFR amplification-negative groups (pooled HR = 1.455, 95% CI 0.852, 2.482, Z = 1.374, P = 0.169). EGFRvIII – Three studies of glioblastoma (21, 31, 32) provided HR data for glioblastoma and EGFRvIII and were included in the analysis. As shown in Fig. 3, significant heterogeneity was present when the data from the three studies were pooled (Cochran Q = 12.47, df = 2, P = 0.002, I2 = 83.96%). The analysis revealed no significant difference in OS between EGFRvIII-positive and EGFRvIII-negative patients (pooled HR = 1.321, 95% CI: 0.881 to 1.981, Z = 1.347, P = 0.178). No studies of anaplastic astrocytoma provided sufficient EGFRvIII data for inclusion in the analysis.
Sensitivity analysis
Results of the sensitivity analysis of EGFR amplification and EGFRvIII using the leave-one-out approach are shown in Figs 4 and 5, respectively. In the analysis of glioblastoma and EGFR amplification, removal of the study by Srividya et al. (30) caused the pooled HR to become significant (P = 0.043) (Fig. 4A). With respect to anaplastic astrocytoma and EGFR amplification, the direction and magnitude of the pooled estimates did not vary considerably when the individual studies were removed in turn, indicating that the meta-analysis had good reliability (Fig. 4B). The analysis of glioblastoma and EGFRvIII showed that when the study by Weller et al. (32) was removed, the pooled HR became significant (P = 0.001; Fig. 5). 313
314 17.90 NA NA NA NA NA NA NA NA 6 NA NA 46 23 NA NA NA NA NA 71 NA
12.30 NA NA NA NA NA NA NA NA 10 NA NA 67 6 NA NA
NA NA NA 43 NA
+
Survival rate (%)
NA NA 19.2 6.9 22.1
13.4 (9.7, 17.0) NA 4.73 NA NA NA 504 days 12 10.5 11.1 NA NA 13.2 14.4 666 days 8
+
HR (95% CI), + vs
NA NA 33.6 34.1 22.9
11.0 (9.5, 12.6) NA 4.8 NA NA NA 458 days 12 2 9.4 NA NA 10.7 20.16 284 days 11 0.69 (0.23, 2.11) 1.24 (0.50, 3.08) 2.5 (1.1, 5.7) NA NA
NA 1.279 NA 0.92 (0.67, 1.27) 1.07 (0.17, 6.89) NA 0.69 NA NA NA 0.39 (0.46–1.40) * 0.881 NA 1.67 (1.03–2.72) NA NA NA NA NA 22 NA
8.80 NA NA NA NA 5% NA NA NA NA NA NA 59 NA NA NA
+
NA NA NA 72 NA
16.90 NA NA NA NA 21% NA NA NA NA NA NA 54 NA NA NA NA NA NA 7.2 NA
11.6 (10.6, 12.5) NA 3.27 NA NA NA NA NA NA NA NA NA 12.4 11.6 NA NA
+
NA NA NA 33 NA
11.9 (10.2, 13.6) NA 4.93 NA NA NA NA NA NA NA NA NA 12.6 16.7 NA NA
Median survival time, months (95% CI)
Median survival time, months (95% CI) Survival rate (%)
OS – EGFRvIII
OS – EGFR amplification
CI, confidence interval; HR, hazard ratio; NA, not available; OS, overall survival. Note, + and refer to EGFR amplification positive and EGFR amplification negative, or EGFRvIII positive or EGFRvIII negative. *Median (range).
Glioblastoma Weller (2014) Bienkowski (2013) Lv (2012) Srividya (2010) Viana-Pereira (2008) Pelloski (2007) Houillier (2006) Layfield (2006) Kleinschmidt-DeMasters (2005) Quan (2005) Shih (2005) Batchelor (2004) Aldape (2004) Shinojima (2003) Hurtt (1992) Torp (1992) Anaplastic astrocytoma Gulati (2010) Kouwenhoven (2009) Idbaih (2008) Aldape (2004) Smith (2001)
First author (year of publication)
Table 2 Summary of study outcomes
NA NA NA NA NA
0.75 (0.44, 1.29) 0.337 NA NA 0.73 (0.13, 4.09) 3.37 (1.74, 6.50) NA NA NA NA NA NA NA NA NA NA
HR (95% CI), + vs
Chen et al.
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Table 3 Modified 18-item Delphi checklist
Y
N
Y
Y
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Y
N
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N
Y
N
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Y
N
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(continued)
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EGFR and glioblastoma prognosis
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13
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1995
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1992
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Chen et al.
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Y
N
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1992
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EGFR and glioblastoma prognosis
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Chen et al. A
B
Figure 2. Forest plot for the meta-analysis of overall survival of EGFR amplification for (A) glioblastoma and (B) anaplastic astrocytoma positive vs negative. CI, confidence interval.
Figure 3. Forest plot for the meta-analysis of overall survival for EGFRvIII-positive vs EGFRvIII-negative glioblastoma. CI, confidence interval.
Publication bias
As five or fewer studies are insufficient to detect funnel plot asymmetry (37), publication bias could not be assessed. Discussion
The results of this meta-analysis to determine whether presence of EGFR amplification or the EGFRvIII mutation has prognostic value in patients with GBM suggest that neither is associated with OS. However, because of the limited 318
number of studies and significant heterogeneity, the current data are not sufficient for determining whether either marker has prognostic value in patients with GBM. Despite the promise of EGFR analysis of resected tissue samples, the overwhelming effect of age, location, tumor morphology (sharp borders for infiltrative borders), resectability, and response to adjuvant treatment with radiotherapy and temazolamide are all more important with respect to prognosis. EGFR analysis may also be biased by the inherent variability in various portions of the tumor where certain cell types and genetic markers may be very heterogeneous.
EGFR and glioblastoma prognosis A
B
Figure 4. Results of sensitivity analysis using the leave-one-out approach to examine the influence of individual studies on pooled estimates of overall survival of EGFR amplification for (A) glioblastoma and (B) anaplastic astrocytoma. OR, odds ratio; CI, confidence interval.
Figure 5. Results of sensitivity analysis using the leave-one-out approach to examine the influence of individual studies on pooled estimates of overall survival for EGFRvIII-positive vs EGFRvIII-negative glioblastoma. OR, odds ratio; CI, confidence interval.
Ligand binding to the EGFR results in cell proliferation, and in normal cells, EGFR activation is tightly regulated (1). Deregulation can occur due to EGFR gene amplification or increased EGFR transcription or translation, which results in cell proliferation (1). EGFR is overexpressed in many malignancies, including those of the lung, colon, and head and neck (38). EGFRvIII is a phosphorylated EGFR mutant that results in the activation of downstream signaling pathways, and subsequent cell proliferation (9). Many studies have been performed attempting to determine whether EGFR amplification or the EGFRvIII mutation has prognostic significance in
patients with GBM, and overall, the results have been inconsistent. Early studies indicated that EGFR gene amplification was associated with a poorer prognosis in patients with GBM (33, 34). However, more recent studies and a meta-analysis have indicated that EGFR amplification had no prognostic value. Layfield et al. (16) reported that EGFR amplification status was not predictive of a favorable or unfavorable prognosis and this finding remained when the data were stratified by sex, age, and performance status. A Cleveland Clinic Foundation study also found that EGFR amplification was not a significant prognostic indicator of OS or radiographic local control in 319
Chen et al. patients with GBM (19). In contrast, Shinojima et al. (20) studied 87 patients with GBM and, on multivariate analysis, found that EGFR amplification was an independent and significant predictor of poorer OS, whereas EGFRvIII overexpression was not predictive of OS. However, in patients with EGFR amplification, EGFRvIII overexpression was an independent and significant predictor or poorer OS. Hobbs et al. (39) have suggested that the behavior of GBM and their response to therapy might vary according to the degree of amplification. A meta-analysis performed in 2000 by Huncharek and Kupelnick (18) concluded that the available data were insufficient for determining whether EGFR gene amplification is of prognostic value in GBM, and the authors pointed out that lack of control for potential confounding factors and known prognostic indicators were lacking in many studies. Younger age is considered to be associated with a better prognosis in patients with GBM. Srividya et al. (30), in a study included in the meta-analysis, found that the prognostic value of EGFR overexpression was correlated with age such that increasing age was associated with a poorer prognosis. Other studies, however, have indicated that younger patients have a poorer prognosis when the tumors exhibit EGFR amplification and that patients more than 60 years of age in which amplification is seen have a more favorable prognosis (20, 27, 39). Kleinschmidt-DeMasters et al. (17) studied 20 patients with more than 75 years of age and found that mean survival time was significantly longer in patients with EGFR amplification (8.3 months) than those without amplification (3.2 months). Disparate results have also been reported with respect to EGFRvIII expression as a prognostic indicator. Weller et al. (32) studied 184 newly diagnosed glioma patients and found that EGFRvIII status was not associated with OS or progression-free survival (PFS) and that it had no prognostic value in patients who received concomitant radiochemotherapy and were free of progression. Aldape et al. (35) examined 44 cases of GBM and found that EGFRvIII positivity was not associated with survival of GBM patients, but was highly associated with reduced survival in anaplastic astrocytoma patients. Bie nkowski et al. (14) reported that EGFRvIII expression was associated with a better prognosis (HR = 0.37) and that EGFR amplification was associated with a worse outcome in younger patients (HR = 3.75) and those that received radiotherapy (HR = 2.71). Furthermore, they 320
found that EGFR amplification was related to a better prognosis when the homozygous CDKN2A deletion was present (HR = 0.12), but to a poorer prognosis where the chromosome 7 polysomy was present (HR = 14.88). Lv et al. (15) also reported difference in survival of patients treated with cetuximab, an EGFR-blocking monoclonal antibody, who had different combinations of EGFR amplification and EGFRvIII expression. These findings underscore the complexity of the molecular pathways involved in cell proliferation, and the interactions between different mutations may help to explain disparate and sometimes contradictory results between studies. While the results of this study do not allow us to conclude whether or not the presence of EGFR amplification or the EGFRvIII mutation has prognostic value in patients with GBM, some studies have suggested that the combination of EGFR with other biomarkers or prognostic factors (e.g. age) may improve its prognostic value (36, 40). Although EGFR may not have prognostic value for GBM, other molecular markers have shown promise. Felsberg et al. (41) reported that MGMT promoter hypermethylation and near-complete tumor resection were the most important parameters associated with a better prognosis in GBM patients. A recent meta-analysis by Dong et al. (42) found that MGMT methylation was strongly correlated with longer OS and disease-free survival in patients with GBM. In another meta-analysis, Zou et al. (43) reported that isocitrate dehydrogenase isoforms 1 and 2 (IDH1/IDH2) mutations were associated with better outcomes in GBM patients. It also remains unclear whether EGFR status is valuable for guiding therapy as clinical trials have indicated that EGFR inhibitors are not effective as expected (44, 45), and investigation of the molecular characteristics of response to EGFR inhibitors is still ongoing (15, 46, 47). Wen et al. (44) studied the effect of erlotinib combined with the mechanistic target of rapamycin inhibitor temsirolimus in patients with recurrent gliomas and reported 6-month PFS rates of only 13% and 8% in GBM and AA patients, respectively. The authors postulated that the minimal antitumor activity may have been the result of insufficient tumor drug levels and a lower than expected maximum tolerated dose of the drugs as a result of increased toxicity. In a trial of bevacizumab in combination with erlotinib for recurrent gliomas, Sathornsumetee et al. (45) reported that the regimen was associated with similar radiographic response and PFS as
EGFR and glioblastoma prognosis other regimens containing bevacizumab. Lv et al. (15) found that GBM patients with EGFR amplification and without EGFRvIII expression treated with cetuximab had significantly better PFS (3.03 vs 1.63 months, P = 0.006) and OS (5.57 vs 3.97 months, P = 0.12) than those that did not receive cetuximab. Mellinghoff et al. (46) studied 49 patients with recurrent GBM and found that co-expression of EGFRvIII and phosphatase and tensin homolog (PTEN) by glioblastoma cells was associated with responsiveness to erlotinib. Similarly, Haas-Kogan et al. (47) found that GBM with high levels of EGFR expression and low levels of phosphorylated protein kinase B (PKB)/Akt had a better response to erlotinib than those with low EGFR expression and high phosphorylated PKB/Akt levels. There are limitations to this study that need to be considered. First is the small number of studies included in the analysis. While there have been many studies performed exploring the value of EGFR amplification and EGFRvIII mutation status as prognostic indicators, few of them have been of high quality and reported relevant data, as mentioned as a limitation of study in this area by the authors of the 2000 meta-analysis (20). There was significant heterogeneity among the included studies, and studies have pointed out that there is marked heterogeneity among tumors and this was not examined in the analysis. Lastly, there are different methods for determining EGFR amplification and EGFRvIII expression, and these were not taken into account in this analysis. In conclusion, the results of this meta-analysis indicate there is insufficient evidence that the presence of either EGFR amplification or the EGFRvIII mutation has prognostic value in patients with GBM. Well-designed studies that account for clinical and molecular pathological factors are necessary to determine the value of these markers in patients with GBM. Acknowledgement None.
Sources of funding None.
Conflicts of interest All authors declare no conflict of interest.
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34. HURTT MR, MOOSSY J, DONOVAN-PELUSO M, LOCKER J. Amplification of epidermal growth factor receptor gene in gliomas: histopathology and prognosis. J Neuropathol Exp Neurol 1992;51:84–90. 35. ALDAPE KD, BALLMAN K, FURTH A et al. Immunohistochemical detection of EGFRvIII in high malignancy grade astrocytomas and evaluation of prognostic significance. J Neuropathol Exp Neurol 2004;63:700–7. 36. BATCHELOR TT, BETENSKY RA, ESPOSITO JM et al. Agedependent prognostic effects of genetic alterations in glioblastoma. Clin Cancer Res 2004;10:228–33. 37. SUTTON AJ, DUVAL SJ, TWEEDIE RL, ABRAMS KR, JONES DR. Empirical assessment of effect of publication bias on meta-analyses. BMJ 2000;320:1574–7. 38. YEWALE C, BARADIA D, VHORA I, PATIL S, MISRA A. Epidermal growth factor receptor targeting in cancer: a review of trends and strategies. Biomaterials 2013;34:8690–707. 39. HOBBS J, NIKIFOROVA MN, FARDO DW et al. Paradoxical relationship between the degree of EGFR amplification and outcome in glioblastomas. Am J Surg Pathol 2012;36:1186–93. M, BOISSELIER B, MOKHTARI K et al. Com40. LABUSSIERE bined analysis of TERT, EGFR, and IDH status defines distinct prognostic glioblastoma classes. Neurology 2014;83:1200–6. 41. FELSBERG J, RAPP M, LOESER S et al. Prognostic significance of molecular markers and extent of resection in primary glioblastoma patients. Clin Cancer Res 2009;15:6683–93. 42. DONG X, LIU RY, CHEN WD. Correlation of promoter methylation in the MGMT gene with glioma risk and prognosis: a meta-analysis. Mol Neurobiol 2014 June 10. Doi:0.1007/s12035-014-8760-3. 43. ZOU P, XU H, CHEN P et al. IDH1/IDH2 mutations define the prognosis and molecular profiles of patients with gliomas: a meta-analysis. PLoS One 2013;8:e68782. 44. WEN PY, CHANG SM, LAMBORN KR et al. Phase I/II study of erlotinib and temsirolimus for patients with recurrent malignant gliomas: North American Brain Tumor Consortium trial 04-02. Neuro Oncol 2014;16:567–78. 45. SATHORNSUMETEE S, DESJARDINS A, VREDENBURGH JJ et al. Phase II trial of bevacizumab and erlotinib in patients with recurrent malignant glioma. Neuro Oncol 2010;12:1300–10. 46. MELLINGHOFF IK, WANG MY, VIVANCO I et al. Molecular determinants of the response of glioblastomas to EGFR kinase inhibitors. N Engl J Med 2005;353:2012–24. 47. HAAS-KOGAN DA, PRADOS MD, TIHAN T et al. Epidermal growth factor receptor, protein kinase B/Akt, and glioma response to erlotinib. J Natl Cancer Inst 2005; 97:880–7.
© 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd ACTA NEUROLOGICA SCANDINAVICA
Prognostic value of epidermal growth factor receptor amplification and EGFRvIII in glioblastoma: meta-analysis Chen J-R, Xu H-Z, Yao Y, Qin Z-Y. Prognostic value of epidermal growth factor receptor amplification and EGFRvIII in glioblastoma: meta-analysis. Acta Neurol Scand 2015: 132: 310–322. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd. Objectives – Epidermal growth factor receptor (EGFR) gene amplification and the EGFRvIII mutation may have prognostic value in patients with glioblastoma. This meta-analysis was to determine whether EGFR gene amplification or the EGFRvIII mutation are predictors of survival in patients with glioblastoma and anaplastic astrocytoma. Materials and methods – Medline, the Cochrane Central Register of Controlled Trials, EMBASE, and Google Scholar databases were searched until July 31, 2014. Studies were selected for inclusion in the analysis if they included patients with anaplastic astrocytoma and/or glioblastoma, EGFR and/or EGFRvIII mutation status was reported, and overall survival (OS) data were reported. Results – Of 113 articles initially identified, only eight contained data with respect to the outcome of interest and were included in the metaanalysis. The number of cases ranged from 14 to 268, and the majority of patients were 60 or more years of age. There was no significant difference in OS between EGFR amplification-positive and EGFR amplification-negative glioblastoma patients (pooled hazard ratio [HR] = 1.101, 95% confidence interval [CI] 0.845, 1.434, P = 0.475) or anaplastic astrocytoma patients (pooled HR = 1.455, 95% CI 0.852, 2.482, P = 0.169). There was no significant difference in OS between EGFRvIII-positive and EGFRvIII-negative glioblastoma patients (pooled HR = 1.321, 95% CI: 0.881–1.981, P = 0.178). Significant heterogeneity existed between the studies, and the significance changed when the analysis was performed with studies removed in turn. Conclusions – There is insufficient evidence that either EGFR amplification or the EGFRvIII mutation has prognostic value in patients with glioblastoma.
Introduction
Glioblastoma multiforme (GBM) is the most common malignant primary brain tumor and has an annual incidence of approximately three cases per 100,000 persons (1, 2). Anaplastic astrocytomas (World Health Organization grade III) account for approximately 10% of all gliomas and exhibit a variable biological behavior (3, 4). Most centers believe that maximal safe resection for eligible patients followed by fractionated radiation therapy and temazolamide represent the 310
J.-R. Chen, H.-Z. Xu, Y. Yao, Z.-Y. Qin Department of Neurosurgery, Huashan Hospital Shanghai Medical College, Fudan University, Shanghai, China
Key words: epidermal growth factor; receptor; epidermal growth factor receptor VIII; glioblastoma; prognosis; survival analysis Z.-Y. Qin, No 12, Middle Wulumuqi Road, Shanghai 200040, China Tel.: +86-21-38719999-2097 Fax: 86-21-50309919 e-mail: [email protected] Accepted for publication March 4, 2015
current standard of care for GBM (5, 6). The prognosis, however, is poor with an overall survival (OS) of 10–12 months (5, 7). For patients with anaplastic astrocytomas, the overall agestandardized 5- and 10-year relative survival rates are 23.6% and 15.1%, respectively (8). The most frequent genetic alteration associated with GBM is amplification of the epidermal growth factor receptor (EGFR) gene (9). Amplification results in overexpression of EGFR, a transmembrane tyrosine kinase receptor. The majority of GBMs with EGFR amplification also
EGFR and glioblastoma prognosis contain EGFRvIII, a mutant EGFR gene that is characterized by the deletion of exons 2 to 7 (9). EGFR is overexpressed in approximately 50–60% of GBMs, and EGFRvIII is found in 24–67% of cases (9, 10). Study of EGFR variations is important as tyrosine kinase inhibitors have shown promise in the treatment of GBM (11). Evidence that EGFR amplification is an independent predictor of survival in patients with GBM varies considerably between studies (1, 10, 12–18). In a previous study, EGFR amplification was not found to be a significant prognostic indicator of OS or radiographic local control in GBM patients treated with surgery (19). On the other hand, Shinojima et al. (20) reported that EGFR amplification was an independent and significant predictor of poorer OS. Other reports have indicated that EGFRvIII overexpression in the presence of EGFR amplification is the strongest indicator of poor survival (16). Contrarily, Bie nkowski et al. (14) reported that EGFRvIII expression was associated with a better prognosis. Other study has suggested that EGFRvIII status defines clinically distinct GBM subsets (21). Thus, the aim of this meta-analysis was to determine whether EGFR gene amplification or the EGFRvIII mutation is an independent predictor of survival in patients with GBM and anaplastic astrocytoma. Materials and methods Search strategy
This systematic review and meta-analysis was conducted in accordance with PRISMA guidelines (22). Medline, the Cochrane Central Register of Controlled Trials, EMBASE, and Google Scholar databases were searched until July 31, 2014 using combinations of the following terms: glioma, GBM, anaplastic astrocytoma, prognostic, prognosis, survival, EGFR, and EGFRvIII mutation. Reference lists of relevant studies were hand-searched. Selection criteria
Studies were selected for inclusion in the analysis if they included patients with anaplastic astrocytoma and/or GBM, EGFR and/or EGFRvIII mutation status was reported, and OS data were reported. Studies in which patients had primary glioma or other types of brain tumors, non-English publications, proceedings, personal communications, letters, comments,
editorials, and case reports were excluded. Studies were identified by the search strategy by two independent reviewers. When there was uncertainty regarding eligibility, a third reviewer was consulted. Data extraction
Data extraction was performed by two independent reviewers, and a third reviewer was consulted for any uncertainties. The following information was extracted from studies that met the inclusion criteria: the name of the first author, year of publication, study design, patient type/disease status, KPS, EGFR amplification and EGFRvIII mutation status, treatment, length of follow-up, and survival outcomes. Quality assessment
The modified 18-item Delphi checklist was used to assess the quality of the included studies (23). Quality assessment was performed by the independent reviewers, and a third reviewer was consulted for any uncertainties. Outcome measures and data analysis
The outcome measure was OS. Hazard ratios (HRs) with 95% confidence intervals (CIs) were calculated for OS in patients who were EGFR amplification positive or EGFRvIII positive compared to patients who were EGFR amplification negative or EGFRvIII negative, respectively. For OS, a HR > 1 indicates the HR is associated with worse survival. Heterogeneity among the studies was assessed by the Cochran Q and the I2 statistic. For Cochran Q, a value of P < 0.10 was considered to indicate statistically significant heterogeneity. For the I2 statistic, no heterogeneity was indicated when I2 = 0–25%, moderate heterogeneity when I2 = 25–50%, large heterogeneity when I2 = 50–75%, and extreme heterogeneity when I2 = 75–100%. A fixed-effects model of analysis was used for this study because of the small number of articles for each outcome (24). Sensitivity analysis using the leave-one-out approach was performed to examine the influence of individual studies on pooled estimates. Pooled HRs were calculated, and a two-sided P-value < 0.05 was considered to indicate statistical significance. All statistical analyses were performed using Comprehensive Meta-Analysis version 2.0 software (Biostat, Englewood, NJ, USA). 311
314 17.90 NA NA NA NA NA NA NA NA 6 NA NA 46 23 NA NA NA NA NA 71 NA
12.30 NA NA NA NA NA NA NA NA 10 NA NA 67 6 NA NA
NA NA NA 43 NA
+
Survival rate (%)
NA NA 19.2 6.9 22.1
13.4 (9.7, 17.0) NA 4.73 NA NA NA 504 days 12 10.5 11.1 NA NA 13.2 14.4 666 days 8
+
HR (95% CI), + vs
NA NA 33.6 34.1 22.9
11.0 (9.5, 12.6) NA 4.8 NA NA NA 458 days 12 2 9.4 NA NA 10.7 20.16 284 days 11 0.69 (0.23, 2.11) 1.24 (0.50, 3.08) 2.5 (1.1, 5.7) NA NA
NA 1.279 NA 0.92 (0.67, 1.27) 1.07 (0.17, 6.89) NA 0.69 NA NA NA 0.39 (0.46–1.40) * 0.881 NA 1.67 (1.03–2.72) NA NA NA NA NA 22 NA
8.80 NA NA NA NA 5% NA NA NA NA NA NA 59 NA NA NA
+
NA NA NA 72 NA
16.90 NA NA NA NA 21% NA NA NA NA NA NA 54 NA NA NA NA NA NA 7.2 NA
11.6 (10.6, 12.5) NA 3.27 NA NA NA NA NA NA NA NA NA 12.4 11.6 NA NA
+
NA NA NA 33 NA
11.9 (10.2, 13.6) NA 4.93 NA NA NA NA NA NA NA NA NA 12.6 16.7 NA NA
Median survival time, months (95% CI)
Median survival time, months (95% CI) Survival rate (%)
OS – EGFRvIII
OS – EGFR amplification
CI, confidence interval; HR, hazard ratio; NA, not available; OS, overall survival. Note, + and refer to EGFR amplification positive and EGFR amplification negative, or EGFRvIII positive or EGFRvIII negative. *Median (range).
Glioblastoma Weller (2014) Bienkowski (2013) Lv (2012) Srividya (2010) Viana-Pereira (2008) Pelloski (2007) Houillier (2006) Layfield (2006) Kleinschmidt-DeMasters (2005) Quan (2005) Shih (2005) Batchelor (2004) Aldape (2004) Shinojima (2003) Hurtt (1992) Torp (1992) Anaplastic astrocytoma Gulati (2010) Kouwenhoven (2009) Idbaih (2008) Aldape (2004) Smith (2001)
First author (year of publication)
Table 2 Summary of study outcomes
NA NA NA NA NA
0.75 (0.44, 1.29) 0.337 NA NA 0.73 (0.13, 4.09) 3.37 (1.74, 6.50) NA NA NA NA NA NA NA NA NA NA
HR (95% CI), + vs
Chen et al.
EGFR and glioblastoma prognosis Table 1 Summary of the studies included in the meta-analysis First author (year of publication)
Number of cases
KPS/WHO performance score
Age (years)
Male (%)
Cohort
184
Cohort Prospective phase II trial Cohort Cohort NA
83 35 140 55 268
Houillier (2006) Layfield (2006)
Cohort Retrospective
220 32
>60: 55% ≤60: 45% 60 (23, 84)* 54 (33, 73)* 47 (18, 65)* 56.1 (27, 79)† 40: 40% 40–60: 36% >60: 24%
54
62
56
KPS, Karnofsky performance status; NA, not available; RCT, randomized controlled trial; WHO, World Health Organization. *Median (range). † Mean (range).
significant different in OS between the EGFR amplification-positive and EGFR amplification-negative groups (pooled HR = 1.455, 95% CI 0.852, 2.482, Z = 1.374, P = 0.169). EGFRvIII – Three studies of glioblastoma (21, 31, 32) provided HR data for glioblastoma and EGFRvIII and were included in the analysis. As shown in Fig. 3, significant heterogeneity was present when the data from the three studies were pooled (Cochran Q = 12.47, df = 2, P = 0.002, I2 = 83.96%). The analysis revealed no significant difference in OS between EGFRvIII-positive and EGFRvIII-negative patients (pooled HR = 1.321, 95% CI: 0.881 to 1.981, Z = 1.347, P = 0.178). No studies of anaplastic astrocytoma provided sufficient EGFRvIII data for inclusion in the analysis.
Sensitivity analysis
Results of the sensitivity analysis of EGFR amplification and EGFRvIII using the leave-one-out approach are shown in Figs 4 and 5, respectively. In the analysis of glioblastoma and EGFR amplification, removal of the study by Srividya et al. (30) caused the pooled HR to become significant (P = 0.043) (Fig. 4A). With respect to anaplastic astrocytoma and EGFR amplification, the direction and magnitude of the pooled estimates did not vary considerably when the individual studies were removed in turn, indicating that the meta-analysis had good reliability (Fig. 4B). The analysis of glioblastoma and EGFRvIII showed that when the study by Weller et al. (32) was removed, the pooled HR became significant (P = 0.001; Fig. 5). 313
314 17.90 NA NA NA NA NA NA NA NA 6 NA NA 46 23 NA NA NA NA NA 71 NA
12.30 NA NA NA NA NA NA NA NA 10 NA NA 67 6 NA NA
NA NA NA 43 NA
+
Survival rate (%)
NA NA 19.2 6.9 22.1
13.4 (9.7, 17.0) NA 4.73 NA NA NA 504 days 12 10.5 11.1 NA NA 13.2 14.4 666 days 8
+
HR (95% CI), + vs
NA NA 33.6 34.1 22.9
11.0 (9.5, 12.6) NA 4.8 NA NA NA 458 days 12 2 9.4 NA NA 10.7 20.16 284 days 11 0.69 (0.23, 2.11) 1.24 (0.50, 3.08) 2.5 (1.1, 5.7) NA NA
NA 1.279 NA 0.92 (0.67, 1.27) 1.07 (0.17, 6.89) NA 0.69 NA NA NA 0.39 (0.46–1.40) * 0.881 NA 1.67 (1.03–2.72) NA NA NA NA NA 22 NA
8.80 NA NA NA NA 5% NA NA NA NA NA NA 59 NA NA NA
+
NA NA NA 72 NA
16.90 NA NA NA NA 21% NA NA NA NA NA NA 54 NA NA NA NA NA NA 7.2 NA
11.6 (10.6, 12.5) NA 3.27 NA NA NA NA NA NA NA NA NA 12.4 11.6 NA NA
+
NA NA NA 33 NA
11.9 (10.2, 13.6) NA 4.93 NA NA NA NA NA NA NA NA NA 12.6 16.7 NA NA
Median survival time, months (95% CI)
Median survival time, months (95% CI) Survival rate (%)
OS – EGFRvIII
OS – EGFR amplification
CI, confidence interval; HR, hazard ratio; NA, not available; OS, overall survival. Note, + and refer to EGFR amplification positive and EGFR amplification negative, or EGFRvIII positive or EGFRvIII negative. *Median (range).
Glioblastoma Weller (2014) Bienkowski (2013) Lv (2012) Srividya (2010) Viana-Pereira (2008) Pelloski (2007) Houillier (2006) Layfield (2006) Kleinschmidt-DeMasters (2005) Quan (2005) Shih (2005) Batchelor (2004) Aldape (2004) Shinojima (2003) Hurtt (1992) Torp (1992) Anaplastic astrocytoma Gulati (2010) Kouwenhoven (2009) Idbaih (2008) Aldape (2004) Smith (2001)
First author (year of publication)
Table 2 Summary of study outcomes
NA NA NA NA NA
0.75 (0.44, 1.29) 0.337 NA NA 0.73 (0.13, 4.09) 3.37 (1.74, 6.50) NA NA NA NA NA NA NA NA NA NA
HR (95% CI), + vs
Chen et al.
6
5
4
3
2
1
disease?
point in the
at a similar
enter the study
Did participants
consecutively?
recruited
participants
Were
appropriate?
explicit and
entry the study
criteria) to
exclusion
(inclusion and
criteria
eligibility
Are the
centre?
more than one
collected in
Were the cases
described?
study
included in the
participants
of the
characteristics
Are the
section?
methods
introduction, or
in the abstract,
clearly stated
of the study
aim/objective
hypothesis/
Is the
Y
N
Y
Y
Y
Y
N
Y
N
Y
Y
2013
2014
Y
Bienkowski
Weller
Y
N
Y
Y
Y
Y
2010
Srividya
Table 3 Modified 18-item Delphi checklist
Y
N
Y
Y
Y
Y
2009
Kouwenhoven
Y
N
Y
N
Y
Y
2008
Idbaih
Y
N
Y
N
Y
Y
2007
Pelloski
Y
N
Y
N
Y
Y
2005
Quan
Y
N
Y
Y
Y
Y
2003
Shinojima
Y
N
Y
Y
Y
Y
2001
Smith
Y
N
Y
N
Y
Y
2006
Layfield
Y
N
Y
Y
Y
Y
2012
Lv
Y
N
Y
N
Y
Y
2011
Hobbs
Y
Y
Y
N
Y
Y
2010
Gulati
Y
N
Y
N
Y
Y
2010
Coulibaly
Viana-
Y
N
Y
N
Y
Y
2008
Pereira
Y
N
Y
N
Y
Y
2006
Houillier
Y
N
Y
N
Y
Y
2005
Shih
Y
N
Y
N
Y
Y
2005
DeMasters
Kleinschmidt-
Y
Y
Y
Y
Y
Y
2004
Batchelor
Y
N
Y
N
Y
Y
1996
Waha
Y
N
Y
N
Y
Y
1995
Diedrich
Torp
Y
N
Y
N
Y
Y
1992
Y
Y
Y
Y
Y
Y
2004
Aldape
(continued)
Y
N
Y
Y
Y
Y
1992
Hurtt
EGFR and glioblastoma prognosis
315
316
13
12
11
10
9
8
7
reported?
of follow-up
Was the length
appropriate?
outcomes
the relevant
used to assess
statistical tests
Were the
intervention?
after
before and
measured
Were outcomes
methods?
or subjective
objective and/
measured with
appropriately
outcomes
Were relevant
section?
methods
introduction or
in the
clearly defined
measures
Are the outcome
in the study?
clearly reported
interventions)
(co-
interventions
Were additional
the study?
described in
clearly
intervention
Was the
Y
Y
N
Y
Y
N
Y
Y
N
Y
Y
N
Y
2013
2014
Y
Bienkowski
Weller
Table 3 (continued)
Y
Y
N
Y
Y
N
Y
2010
Srividya
Y
Y
N
Y
Y
N
Y
2009
Kouwenhoven
Y
Y
N
Y
Y
N
Y
2008
Idbaih
Y
Y
N
Y
Y
N
Y
2007
Pelloski
Y
Y
N
Y
Y
N
N
2005
Quan
Y
Y
N
Y
Y
N
Y
2003
Shinojima
Y
Y
N
Y
Y
N
N
2001
Smith
Y
Y
N
Y
Y
N
Y
2006
Layfield
Y
Y
N
Y
Y
N
Y
2012
Lv
Y
Y
N
Y
Y
N
Y
2011
Hobbs
Y
Y
N
Y
Y
N
Y
2010
Gulati
Y
Y
N
Y
Y
N
Y
2010
Coulibaly
Viana-
Y
Y
N
Y
Y
N
N
2008
Pereira
Y
Y
N
Y
Y
N
N
2006
Houillier
Y
Y
N
Y
Y
N
Y
2005
Shih
Y
Y
N
Y
Y
N
Y
2005
DeMasters
Kleinschmidt-
Y
Y
N
Y
Y
N
Y
2004
Batchelor
Y
Y
N
Y
Y
N
Y
1996
Waha
Y
Y
N
Y
Y
N
N
1995
Diedrich
Torp
Y
Y
N
Y
Y
N
Y
1992
Y
Y
N
Y
Y
N
Y
2004
Aldape
(continued)
Y
Y
N
Y
Y
N
Y
1992
Hurtt
Chen et al.
study reported?
support for the
source of
interest and
competing
Are both
results?
supported by
the study
conclusions of
Are the
reported?
events
Are adverse
outcomes?
relevant
analysis of
the data
variability in
the random
estimates of
provide
Does the study
reported?
follow-up
Was the loss to
Y, yes; N, no.
18
17
16
15
14
Y
Y
N
Y
Y
Y
N
Y
N
2013
2014
N
Bienkowski
Weller
Table 3 (continued)
Y
Y
N
Y
N
2010
Srividya
Y
Y
N
Y
N
2009
Kouwenhoven
Y
Y
N
Y
N
2008
Idbaih
Y
Y
N
Y
N
2007
Pelloski
N
Y
N
Y
N
2005
Quan
Y
Y
N
Y
N
2003
Shinojima
Y
Y
N
Y
N
2001
Smith
N
Y
N
Y
N
2006
Layfield
Y
Y
N
Y
Y
2012
Lv
Y
Y
N
Y
N
2011
Hobbs
N
Y
N
Y
N
2010
Gulati
Y
Y
N
Y
N
2010
Coulibaly
Viana-
N
Y
N
Y
Y
2008
Pereira
N
Y
N
Y
N
2006
Houillier
Y
Y
N
Y
N
2005
Shih
N
Y
N
Y
N
2005
DeMasters
Kleinschmidt-
Y
Y
N
Y
N
2004
Batchelor
N
Y
N
Y
N
1996
Waha
Y
Y
N
Y
N
1995
Diedrich
Torp
Y
Y
N
Y
N
1992
Y
Y
N
Y
N
1992
Hurtt
Y
Y
N
Y
N
2004
Aldape
EGFR and glioblastoma prognosis
317
Chen et al. A
B
Figure 2. Forest plot for the meta-analysis of overall survival of EGFR amplification for (A) glioblastoma and (B) anaplastic astrocytoma positive vs negative. CI, confidence interval.
Figure 3. Forest plot for the meta-analysis of overall survival for EGFRvIII-positive vs EGFRvIII-negative glioblastoma. CI, confidence interval.
Publication bias
As five or fewer studies are insufficient to detect funnel plot asymmetry (37), publication bias could not be assessed. Discussion
The results of this meta-analysis to determine whether presence of EGFR amplification or the EGFRvIII mutation has prognostic value in patients with GBM suggest that neither is associated with OS. However, because of the limited 318
number of studies and significant heterogeneity, the current data are not sufficient for determining whether either marker has prognostic value in patients with GBM. Despite the promise of EGFR analysis of resected tissue samples, the overwhelming effect of age, location, tumor morphology (sharp borders for infiltrative borders), resectability, and response to adjuvant treatment with radiotherapy and temazolamide are all more important with respect to prognosis. EGFR analysis may also be biased by the inherent variability in various portions of the tumor where certain cell types and genetic markers may be very heterogeneous.
EGFR and glioblastoma prognosis A
B
Figure 4. Results of sensitivity analysis using the leave-one-out approach to examine the influence of individual studies on pooled estimates of overall survival of EGFR amplification for (A) glioblastoma and (B) anaplastic astrocytoma. OR, odds ratio; CI, confidence interval.
Figure 5. Results of sensitivity analysis using the leave-one-out approach to examine the influence of individual studies on pooled estimates of overall survival for EGFRvIII-positive vs EGFRvIII-negative glioblastoma. OR, odds ratio; CI, confidence interval.
Ligand binding to the EGFR results in cell proliferation, and in normal cells, EGFR activation is tightly regulated (1). Deregulation can occur due to EGFR gene amplification or increased EGFR transcription or translation, which results in cell proliferation (1). EGFR is overexpressed in many malignancies, including those of the lung, colon, and head and neck (38). EGFRvIII is a phosphorylated EGFR mutant that results in the activation of downstream signaling pathways, and subsequent cell proliferation (9). Many studies have been performed attempting to determine whether EGFR amplification or the EGFRvIII mutation has prognostic significance in
patients with GBM, and overall, the results have been inconsistent. Early studies indicated that EGFR gene amplification was associated with a poorer prognosis in patients with GBM (33, 34). However, more recent studies and a meta-analysis have indicated that EGFR amplification had no prognostic value. Layfield et al. (16) reported that EGFR amplification status was not predictive of a favorable or unfavorable prognosis and this finding remained when the data were stratified by sex, age, and performance status. A Cleveland Clinic Foundation study also found that EGFR amplification was not a significant prognostic indicator of OS or radiographic local control in 319
Chen et al. patients with GBM (19). In contrast, Shinojima et al. (20) studied 87 patients with GBM and, on multivariate analysis, found that EGFR amplification was an independent and significant predictor of poorer OS, whereas EGFRvIII overexpression was not predictive of OS. However, in patients with EGFR amplification, EGFRvIII overexpression was an independent and significant predictor or poorer OS. Hobbs et al. (39) have suggested that the behavior of GBM and their response to therapy might vary according to the degree of amplification. A meta-analysis performed in 2000 by Huncharek and Kupelnick (18) concluded that the available data were insufficient for determining whether EGFR gene amplification is of prognostic value in GBM, and the authors pointed out that lack of control for potential confounding factors and known prognostic indicators were lacking in many studies. Younger age is considered to be associated with a better prognosis in patients with GBM. Srividya et al. (30), in a study included in the meta-analysis, found that the prognostic value of EGFR overexpression was correlated with age such that increasing age was associated with a poorer prognosis. Other studies, however, have indicated that younger patients have a poorer prognosis when the tumors exhibit EGFR amplification and that patients more than 60 years of age in which amplification is seen have a more favorable prognosis (20, 27, 39). Kleinschmidt-DeMasters et al. (17) studied 20 patients with more than 75 years of age and found that mean survival time was significantly longer in patients with EGFR amplification (8.3 months) than those without amplification (3.2 months). Disparate results have also been reported with respect to EGFRvIII expression as a prognostic indicator. Weller et al. (32) studied 184 newly diagnosed glioma patients and found that EGFRvIII status was not associated with OS or progression-free survival (PFS) and that it had no prognostic value in patients who received concomitant radiochemotherapy and were free of progression. Aldape et al. (35) examined 44 cases of GBM and found that EGFRvIII positivity was not associated with survival of GBM patients, but was highly associated with reduced survival in anaplastic astrocytoma patients. Bie nkowski et al. (14) reported that EGFRvIII expression was associated with a better prognosis (HR = 0.37) and that EGFR amplification was associated with a worse outcome in younger patients (HR = 3.75) and those that received radiotherapy (HR = 2.71). Furthermore, they 320
found that EGFR amplification was related to a better prognosis when the homozygous CDKN2A deletion was present (HR = 0.12), but to a poorer prognosis where the chromosome 7 polysomy was present (HR = 14.88). Lv et al. (15) also reported difference in survival of patients treated with cetuximab, an EGFR-blocking monoclonal antibody, who had different combinations of EGFR amplification and EGFRvIII expression. These findings underscore the complexity of the molecular pathways involved in cell proliferation, and the interactions between different mutations may help to explain disparate and sometimes contradictory results between studies. While the results of this study do not allow us to conclude whether or not the presence of EGFR amplification or the EGFRvIII mutation has prognostic value in patients with GBM, some studies have suggested that the combination of EGFR with other biomarkers or prognostic factors (e.g. age) may improve its prognostic value (36, 40). Although EGFR may not have prognostic value for GBM, other molecular markers have shown promise. Felsberg et al. (41) reported that MGMT promoter hypermethylation and near-complete tumor resection were the most important parameters associated with a better prognosis in GBM patients. A recent meta-analysis by Dong et al. (42) found that MGMT methylation was strongly correlated with longer OS and disease-free survival in patients with GBM. In another meta-analysis, Zou et al. (43) reported that isocitrate dehydrogenase isoforms 1 and 2 (IDH1/IDH2) mutations were associated with better outcomes in GBM patients. It also remains unclear whether EGFR status is valuable for guiding therapy as clinical trials have indicated that EGFR inhibitors are not effective as expected (44, 45), and investigation of the molecular characteristics of response to EGFR inhibitors is still ongoing (15, 46, 47). Wen et al. (44) studied the effect of erlotinib combined with the mechanistic target of rapamycin inhibitor temsirolimus in patients with recurrent gliomas and reported 6-month PFS rates of only 13% and 8% in GBM and AA patients, respectively. The authors postulated that the minimal antitumor activity may have been the result of insufficient tumor drug levels and a lower than expected maximum tolerated dose of the drugs as a result of increased toxicity. In a trial of bevacizumab in combination with erlotinib for recurrent gliomas, Sathornsumetee et al. (45) reported that the regimen was associated with similar radiographic response and PFS as
EGFR and glioblastoma prognosis other regimens containing bevacizumab. Lv et al. (15) found that GBM patients with EGFR amplification and without EGFRvIII expression treated with cetuximab had significantly better PFS (3.03 vs 1.63 months, P = 0.006) and OS (5.57 vs 3.97 months, P = 0.12) than those that did not receive cetuximab. Mellinghoff et al. (46) studied 49 patients with recurrent GBM and found that co-expression of EGFRvIII and phosphatase and tensin homolog (PTEN) by glioblastoma cells was associated with responsiveness to erlotinib. Similarly, Haas-Kogan et al. (47) found that GBM with high levels of EGFR expression and low levels of phosphorylated protein kinase B (PKB)/Akt had a better response to erlotinib than those with low EGFR expression and high phosphorylated PKB/Akt levels. There are limitations to this study that need to be considered. First is the small number of studies included in the analysis. While there have been many studies performed exploring the value of EGFR amplification and EGFRvIII mutation status as prognostic indicators, few of them have been of high quality and reported relevant data, as mentioned as a limitation of study in this area by the authors of the 2000 meta-analysis (20). There was significant heterogeneity among the included studies, and studies have pointed out that there is marked heterogeneity among tumors and this was not examined in the analysis. Lastly, there are different methods for determining EGFR amplification and EGFRvIII expression, and these were not taken into account in this analysis. In conclusion, the results of this meta-analysis indicate there is insufficient evidence that the presence of either EGFR amplification or the EGFRvIII mutation has prognostic value in patients with GBM. Well-designed studies that account for clinical and molecular pathological factors are necessary to determine the value of these markers in patients with GBM. Acknowledgement None.
Sources of funding None.
Conflicts of interest All authors declare no conflict of interest.
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