Final Results of ERBIMOX: A Randomized Phase II Study of Modified FOLFOX7 With or Without Cetuximab as First-Line Treatment for KRAS Wild-type Metastatic Colorectal Cancer.

Background: The combination of FOLFOX/FOLFIRI with an EGFR-antibody (cetuximab/panitumumab) is a first-line standard for RAS wild-type metastatic colorectal cancer (mCRC). The OPTIMOX stop-and-go regimen, which reduces oxaliplatin-induced neuropathy, and fluorouracil/folinic acid (FU/FA) were standard maintenance-therapies in the pre-antibody era. Whether an EGFR-antibody adds value to the OPTIMOX strategy in the RAS wild-type setting remains unknown.

Methods: In the open-label, randomized, multicenter phase II ERBIMOX trial, patients with KRAS wild-type mCRC received either first-line induction-therapy with 8 cycles of mFOLFOX7 followed by maintenance-therapy with FU/FA (OPTIMOX arm) or mFOLFOX7 + cetuximab followed by FU/FA + cetuximab (ERBIMOX arm). Primary objective was to demonstrate superiority of additional cetuximab to mFOLFOX7 during induction/maintenance-therapy. Primary endpoint was objective response rate (ORR). Secondary endpoints included progression-free survival (PFS), overall survival (OS) and safety. The trial is registered at EudraCT (No.2006-002744-28).

Results: From 2006-2011, 138 patients with KRAS wild-type mCRC from 23 German sites were randomly assigned to either OPTIMOX (N = 63) or ERBIMOX (N = 75). ORR numerically favored the ERBIMOX arm (64.0% vs. 54.0%, P = 0.3071). Median PFS (ERBIMOX vs. OPTIMOX) was 9.6 vs. 8.8 months (P = 0.7612), median OS 25.6 vs. 30.9 months (P = 0.5821). Most common grade 3/4 adverse events (AEs) were skin reactions (21.9% vs. 2.1%) and gastrointestinal disorders (13.5% vs. 9.5%). No cetuximab-related deaths occurred.

Conclusion: In treatment-naïve KRAS wild-type mCRC, adding cetuximab to mFOLFOX7 resulted in numerically higher ORR than mFOLFOX alone, but no statistically significant differences in ORR, PFS or OS; probably because of the premature stop due to poor recruitment. The safety profile was as expected, with few discontinuations.