Retrospective RAS analysis of the EPIC trial: Cetuximab plus irinotecan vs irinotecan in patients (pts) with second-line metastatic colorectal cancer (mCRC)

Abstract

Background: The multicenter, open‐label, randomized, phase 3 EPIC study (EMR 062202‐025) investigated the addition of cetuximab to irinotecan vs irinotecan in pts with EGFR‐expressing mCRC who had previously progressed on first‐line fluoropyrimidine‐ and oxaliplatin‐based chemotherapy. The primary endpoint was overall survival (OS). We present the extended RAS analysis (KRAS/NRAS exons 2, 3, and 4) for the EPIC study population. Methods: 1298 RAS‐unselected pts were enrolled from May 2003 to February 2006. Existing DNA samples were reanalyzed using BEAMing (beads, emulsion, amplification, magnetics) technology. RAS wild‐type (wt) status was defined as having all alleles be analyzable and a sum of RAS mutations of≤5%. Baseline characteristics, efficacy, safety, and post‐study therapy were assessed. 10.3% had no RAS data available. Results: Among the 452 (231 in the cetuximab + irinotecan arm and 221 in the irinotecan arm) pts with RAS wt mCRC, baseline characteristics were comparable to those of the unselected population. 67.5% had 1 prior line of therapy. In the cetuximab + irinotecan vs irinotecan arms, median progression‐free survival (PFS) was 5.4 vs 2.6 months (HR, 0.57 [95% CI, 0.46‐0.69]; P< .0001), median OS was 12.3 vs 12.0 months (HR, 0.91 [95% CI, 0.71‐1.17; P= .4645]), and overall response rate (ORR) was 29.4% vs 5.0% (OR, 8.12 [95% CI, 4.04‐17.40]; P< .0001), respectively. 76.4% and 61.8% of pts in the cetuximab +irinotecan vs irinotecan arms, respectively, experienced a grade≥ 3 adverse event. 47.1% of pts in the irinotecan arm received cetuximab in a subsequent line of therapy vs 11.3% in the cetuximab + irinotecan arm. Conclusions: This retrospective analysis confirms that cetuximab‐based therapy is suitable as a standard, second‐line treatment for pts with RAS wt mCRC. Specifically, the addition of cetuximab to irinotecan significantly improved PFS and ORR in this population. A large proportion of pts in the irinotecan arm crossed over to receive post‐study cetuximab, potentially masking any OS benefit of the addition of cetuximab to irinotecan in this study. Benefits appear clinically relevantly higher than for pts with RAS‐unselected or KRAS wt mCRC.