Genetic Polymorphisms of FcγRIIa and FcγRIIIa Are Not Predictive of Clinical Outcomes after Cetuximab plus Irinotecan Chemotherapy in Patients with Metastatic Colorectal Cancer

vival (p < 0.001). Fc gamma RIIaH/H, H/R and R/R polymorphisms were observed in 54, 49 and 4 patients, respectively, and Fc gamma RIIIa V/V, V/F and F/F polymorphisms were observed in 6, 65, and 36 patients, respectively. Clinical outcomes were not significantly associated with either Fc gamma RIIa or Fc gamma RIIIa polymorphisms or with combinations of K RAS status and Fc gamma R polymorphisms. Conclusion: The Fc gamma RIIa and Fc gamma RIIIa polymorphisms may not be useful molecular biomarkers for the activity of cetuximab in patients with mCRC. Copyright (C) 2012 S. Karger AG, BaselObjective: The anti-epidermal growth factor receptor monoclonal antibody cetuximab has been shown to be effective in patients with wild-type KRAS metastatic colorectal cancer (mCRC). Fragment C gamma receptor (Fc gamma R) polymorphisms may predict the effectiveness of cetuximab, but this has not been established. This study investigated the clinical relevance of Fc gamma R gene polymorphisms and KRAS status in irinotecan-refractory mCRC patients treated with cetuximab. Methods: The total number of irinotecan-refractory mCRC patients studied was 118. Among them, 117 and 107 patients were screened for KRAS mutations and genetic polymorphisms of Fc gamma RIIa-131H/R and Fc gamma RIIIa-158V/F, respectively. The association of Fc gamma R polymorphisms and KRAS mutations with clinical outcome was analyzed. Results: KRAS mutations were found in 33 patients (27.1%). Wild-type KRAS was associated with a better response rate (p < 0.001), longer progression-free survival (p < 0.001) and longer overall sur