Efficacy of panitumumab plus irinotecan versus cetuximab plus irinotecan in patients with wild-type KRAS exon2 metastatic colorectal cancer previously treated with bevacizumab within 6 months.

800Background: The ASPECCT study showed panitumumab (Pmab) is non-inferior to cetuximab (Cmab) for chemotherapy-refractory and intolerant wild-type (WT) KRAS exon2 metastatic colorectal cancer (mCRC). In the subgroup analysis, Pmab provided more favorable outcomes than Cmab for patients (pts) previously treated with bevacizumab (Bmab). However, some reports suggested that anti-EGFR antibody (anti-EGFR) efficacy was reduced when received within 6 months of last administration of Bmab. In this study, we aim to evaluate the difference in efficacy between Pmab and Cmab in pts who received prior Bmab and were treated with anti-EGFR after a short interval. Methods: We retrospectively evaluated pts treated with anti-EGFR and irinotecan (IRI) after failure of Bmab, fluoropyrimidine, oxaliplatin, and IRI at two institutions. The main inclusion criteria were WT KRAS exon2 mCRC, ECOG PS 0-2, and no prior administration of anti-EGFR within 6 months after Bmab. Results: From Sep. 2008 to Mar. 2016, 124 consecutive pts...