Retrospective analysis of overall survival (OS) by subsequent therapy in patients (pts) with RAS wild-type (wt) metastatic colorectal cancer (mCRC) receiving irinotecan ± cetuximab in the EPIC study.

3580 Background: The multicenter, open-label, randomized, phase 3 EPIC study (EMR 062202-025) investigated cetuximab + irinotecan vs irinotecan as a second-line (2L) therapy in pts with EGFR-detectable mCRC. A retrospective analysis in the EPIC RAS wt population showed improved overall response rate (29.4% vs 5.0%) and progression-free survival (5.4 vs 2.6 mo) upon the addition of cetuximab to irinotecan. Median OS (mOS) was similar in both treatment arms, possibly due to differences in subsequent therapies. We present OS by post-study therapy in the RAS wt population. Methods: 1298 RAS-unselected pts were enrolled from May 2003 to February 2006. The primary endpoint was OS. RAS status was determined retrospectively in 2018 from existing DNA samples using BEAMing technology; wt status was defined as having a sum of mutated RAS allele frequencies of ≤5%, with all relevant alleles being analyzable. Results: Among the 452 pts with RAS wt mCRC, 231 received cetuximab + irinotecan and 221 received irinotecan. Baseline characteristics were similar in both arms. OS data by post-study therapy are summarized in the Table. No new or unexpected safety signals were observed. Conclusions: Post-study cetuximab was associated with improved OS in both treatment arms compared with post-study therapy without cetuximab and no subsequent therapy, suggesting that cetuximab-based therapy may be suitable as a standard treatment for pts with RAS wt mCRC in the rechallenge setting. Study limitations include a potential bias due to the differences in proportion of subsequent therapies with and without cetuximab between arms (almost 50% of pts in the irinotecan arm received post-study cetuximab) as well as the likelihood for pts who live longer to receive cetuximab in any subsequent therapy line. [Table: see text]