EGFR, Cox-2, and EGF polymorphisms associated with progression-free survival of EGFR-expressing metastatic colorectal cancer patients treated with single-agent cetuximab (IMCL-0144)

Abstract

4129 Background: A phase II study of cetuximab (IMCL-0144) has shown response rate of 12 % in patients with EGFR expressing metastatic colorectal cancer (mCRC). Recently, we reported that polymorphisms in the EGFR pathway may be useful molecular markers to predict clinical outcome. In this larger study, we tested whether polymorphisms in genes involved in the EGFR and angiogenesis pathway will be associated with clinical outcome. Methods: We analyzed 136 tissue samples from 346 mCRC pts enrolled in the phase II study of cetuximab (IMCL-0144), 133 cases were informative. The response rate in these 133 pts was 10% with a median progression-free survival (PFS) of 1.3 months (95% CI, 1.2 to 1.5) and an overall survival time (OS) of 5.5 months (95% CI, 4.1 to 7.5). Gr3–4 toxicity was observed in 56%. Gene polymorphisms of EGFR, Cox-2, EGF, cyclin D1, fragment c γ receptor 2A (FCGR2A), FCGR3A, VEGF, IL-8 were assessed from gDNA extracted from tissue samples by using PCR-based RFLP technique. Univariate analysis (Fisher’s exact test for response; log-rank test for PFS and OS) was performed to examine associations between polymorphisms and clinical outcome. A classification and regression tree (CART) analysis was used to identify subgroups of patients who were more likely to benefit from cetuximab. Results: Pts with EGFR G497C GA, Cox-2 G-765C CC, EGF A61G GG genotype showed better PFS (p=0.02, 1.8mo. vs. 1.2mo.; p=0.03, 6.9mo. vs. 1.3mo.; p=0.04, 1.4mo. vs. 1.2mo.), respectively. We found trends in associations between Cox-2 and tumor response (p=0.09), between EGF and Gr3–4 toxixity (p=0.06). CART analyses indicated that germline polymorphisms in EGFR, EGF, Cox-2, Cyclin D1, IL-8, FCGR2A and FCGR3A genes could be used to identify patients who benefit most likely of cetuximab therapy. Conclusions: Our data suggest that the polymorphisms of EGFR, Cox-2, and EGF may be useful molecular markers to predict clinical outcome in mCRC pts treated with single-agent cetuximab. And prospective studies will need to be done to confirm these preliminary findings. [Table: see text]