Impact of EGFR amplification status in newly diagnosed glioblastoma treated with Stupp protocol.

Abstract

e13569 Background: Standard post-surgical glioblastoma (GBM) treatment, per Stupp protocol, includes six-weeks of concurrent Temozolomide chemoradiation followed by at least six cycles of adjuvant-Temozolomide. Previous investigations into epidermal growth factor receptor (EGFR) amplification as a prognostic factor in GBM have yielded contradicting results, requiring further investigation. The primary aim of this study was to determine the degree to which EGFR amplification, in newly diagnosed GBM, impacted progression free survival (PFS) and overall survival (OS). Methods: Data from 582 patients who underwent surgical intervention for GBM at a tertiary care institution between 2012 and 2018 were analyzed. Only adult patients who underwent treatment per Stupp protocol and had pathological analysis on EGFR and CEP7 were included. Amplification and non-amplification status was calculated by a ratio of EGFR/CEP7 > 2 and < 2, respectively. PFS and OS outcomes were compared using Cox proportional hazard models stratified by surgery type and sex. Results: Of the original 582 patients, 122 were treated per Stupp protocol and had documented EGFR analysis. Of patients who were EGFR amplified, 41 (58.5%) were male and 25 (48.1%) were female (p = 0.38) and median amplification was 1.07 and 1.16 (p < 0.001), respectively. EGFR non-amplified patients had a PFS hazard ratio, HR = 0.70 (95% CI = 0.44 – 1.12, p = 0.14); and an OS HR = 0.60 (95% CI = 0.35 – 1.03, p = 0.065). When the EGFR/CEP7 ratio was stratified by quartile, it was found that Q4 compared to Q1 (Q4 > 6.50 vs 0 < Q1 ≤ 1.06) had a PFS HR = 2.1 (95% CI = 1.11 – 4.07, p = 0.024); and an OS HR = 2.48 (95% CI = 1.10 – 5.60, p = 0.028). Conclusions: There was no statistical difference in prevalence of EGFR amplification by sex. However, despite statistical significance, there was minimal difference in median degree of amplification by sex (0.09). Trends begin to show that patients who were EGFR non-amplified had better PFS and OS outcomes than patients who were EGFR amplified, although this was not statistically significant. Patients with very high EGFR amplification (Q4) had significantly poorer PFS and OS outcomes than patients with very low EGFR amplification (Q1).