Purpose

The antiepidermal growth factor receptor antibody cetuximab shows activity in irinotecanrefractory metastatic colorectal cancer (mCRC), mainly in wild-type KRAS tumors. Cetuximab may also exert antitumor effects through antibody-dependent cell-mediated cytotoxicity (ADCC) in which antibody Fc portion interacts with Fc receptors (FcRs) expressed by immune cells. ADCC is influenced by FcRIIa-H131R and FcRIIIa-V158F polymorphisms that are clinically relevant in follicular lymphoma and metastatic breast cancer treated with rituximab and trastuzumab, respectively. We investigated the association of FcR polymorphisms and KRAS mutation with the outcome of irinotecan-refractory mCRC patients treated with cetuximab plus irinotecan.