Extended RAS Analysis of the Phase III EPIC Trial: Irinotecan + Cetuximab Versus Irinotecan as Second‐Line Treatment for Patients with Metastatic Colorectal Cancer

BACKGROUND: The multicenter, open‐label, randomized, phase III EPIC study (EMR 062202‐025) investigated cetuximab plus irinotecan versus irinotecan in patients with epidermal growth factor receptor–detectable metastatic colorectal cancer (mCRC) that progressed on first‐line fluoropyrimidine‐ and oxaliplatin‐based chemotherapy; we report the outcomes of patients with RAS‐wild‐type (wt) disease. MATERIALS AND METHODS: Available DNA samples from RAS‐unselected patients (n = 1,164 of 1,298 [89.7%]) were reanalyzed for RAS mutations using beads, emulsion, amplification, and magnetics. Baseline characteristics, efficacy, safety, and poststudy therapy were assessed. RAS‐wt status was defined as a mutated RAS allele frequency of ≤5%, with all relevant alleles being analyzable. RESULTS: Baseline characteristics were comparable between the groups (n = 452 patients with RAS‐wt mCRC; cetuximab plus irinotecan n = 231, irinotecan n = 221) and between the RAS‐wt and RAS‐unselected populations. In the cetuximab plus irinotecan versus irinotecan arms, median overall survival was 12.3 versus 12.0 months, median progression‐free survival (PFS) was 5.4 versus 2.6 months, and objective response rate (ORR) was 29.4% versus 5.0%, respectively. Quality of life (QoL) was improved in the cetuximab plus irinotecan arm. Serious adverse events occurred in 45.4% (cetuximab plus irinotecan) and 42.4% (irinotecan) of patients. In total, 47.1% of patients in the irinotecan arm received subsequent cetuximab therapy. CONCLUSION: PFS, ORR, and QoL were improved with cetuximab plus irinotecan as a second‐line treatment in patients with RAS‐wt mCRC, confirming that cetuximab‐based therapy is suitable in this population. Almost half of patients in the irinotecan arm received poststudy cetuximab, masking a potential overall survival benefit of cetuximab addition. IMPLICATIONS FOR PRACTICE: Cetuximab is approved for the treatment of RAS–wild‐type metastatic colorectal cancer (mCRC). In this retrospective analysis of the phase III EPIC study (cetuximab plus irinotecan vs. irinotecan alone as second‐line treatment in patients with RAS‐unselected mCRC), the subgroup of patients with RAS–wild‐type mCRC who received cetuximab plus irinotecan had improved progression‐free survival, objective response rate, and quality of life compared with the RAS‐unselected population. These findings suggest that cetuximab‐based therapy is a suitable second‐line treatment for patients with RAS–wild‐type mCRC.