The Role of KRAS Mutations in Predicting the Efficacy of Cetuximab-Plus-Irinotecan Therapy in Irinotecan-Refractory Korean Metastatic Colorectal Cancer Patients

Objective: This study evaluated the clinical relevance of KRAS and BRAF mutational status in 66 irinotecan-refractory Korean metastatic colorectal cancer (mCRC) patients treated with cetuximab-plus-irinotecan-based chemotherapy. Methods: A total of 66 irinotecan-refractory mCRC patients treated with cetuximab-plus-irinotecan-based chemotherapy were included. Tumors were screened for KRAS mutations (codons 12 and 13) and a BRAF mutation (V600E) using direct sequencing and the Snapshot assay. Results: The objective response rate (RR) for treatment was 21.2% (14/66) and skin rashes were observed in 43 (65.2%) of the 66 patients. A KRAS mutation was detected in 27 (40.9%) tumors, and was associated with lower RR (wild-type vs. mutated KRAS : 33.3 vs. 3.7%, p = 0.005) and shorter progression-free survival (PFS) and overall survival (OS; PFS: 6.4 vs. 2.0 months, p = 0.005; OS: 17.8 vs. 7.1 months, p = 0.001). Severe skin toxicity was associated with better RR and longer PFS and OS. BRAF mutations were not detected. Multivariate analysis revealed that KRAS status and skin toxicity were independent predictive factors of PFS and OS. Conclusions: This study indicates the clinical relevance of KRAS mutations in predicting the efficacy of cetuximab-plus-irinotecan-based chemotherapy in irinotecan-refractory Korean mCRC patients. Copyright (C) 2009 S. Karger AG, Basel