Molecular marker assessments for epidermal growth factor receptor (EGFR) expression by immunohistochemistry (IHC) and histoscore (H-score) in the phase III SELECT trial.

Abstract

8052 Background: SELECT was a phase III study that investigated whether the addition of cetuximab (C) to pemetrexed (P) improved outcome in previously treated patients (pts) with recurrent or progressive non-small cell lung cancer (NSCLC). Clinical results have been reported previously and demonstrated that adding C to P did not improve progression-free survival (PFS) or overall survival (OS). H-score has been reported to be a potential predictor of outcome for C therapy. Prespecified biomarker analyses, including EGFR IHC and H-score, are reported here. Methods: EGFRexpression in tumor tissue was not required for eligibility; however, tissue was collected and analyzed for EGFR expression by IHC using standard methods. In addition, H-score evaluation was performed by trained central pathologists and correlated with clinical outcome using a predefined cutoff for “low” and “high” of <200 and ≥200, respectively. Results: A total of 449 (IHC) and 406 (H-score) pt specimens were evaluable. Demographics for pts with tissue available for EGFR analysis were similar to the overall population. For IHC+ pts (n=396), median PFS for C+P was 3.02 months (95% CI, 2.76–3.45) compared with 2.99 months (95% CI, 2.63–4.14) for P (HR, 1.02 [95% CI, 0.83–1.24]; p=.86). For pts with low H-score (N=99 [C+P] and N=111 [P]), median PFS was 2.7 months (95% CI, 1.8–3.2) with C+P and 3.1 months (95% CI, 2.6–4.1) with P (HR, 1.11 [95% CI, 0.84–1.46]; P=.48); median OS was 6.7 months (95% CI, 5.3–8.6) with C+P and 6.6 months (95% CI, 4.7–9.2) with P (HR, 0.96 [95% CI, 0.72–1.27]; P=.76). Among pts with high H-scores (N=101 [C+P] and N= 95 [P]), median PFS was 3.2 months (95% CI, 2.7–4.6) with C+P and 3.7 months (95% CI, 1.7–4.5) with P (HR, 1.02 [95% CI, 0.77–1.37]; P=.86); median OS was 7.7 months (95% CI, 6.5–10.9) with C+P and 8.0 months (95% CI, 7.0–9.1) with P (HR, 1.17 [95% CI, 0.86–1.57]; P=.32). Conclusions: EGFR H-score was not predictive of benefit for the addition of C to P in this population of pts with NSCLC. There was also no treatment effect in the IHC+ group. Clinical trial information: NCT00095199.