We retrospectively collected the clinical data of KRAS exon 2 wild type (WT) mCRC patients treated with EGFR inhibitor monotherapy or EGFR inhibitor plus irinotecan as third-line chemotherapy. The association between primary tumor location, RAS (KRAS exon 3, 4 or NRAS), BRAF V600E, and PIK3CA mutational status, and treatment outcome was evaluated….In multivariate analysis, RAS (p=0.004) and BRAF mutations (p=0.00008) were independent factors for shorter PFS. Poor performance status (p=0.01) and BRAF mutation (p=0.00002) were independent factors for shorter OS...