Retrospective cohort study on the safety and efficacy of panitumumab for patients with metastatic colorectal cancer: The HGCSG1002 study—Analysis of after cetuximab refractory.

541 Background: In the previous studies, panitumumab (Pmab) has been demonstrated the efficacy for patients with metastatic colorectal cancer (mCRC) in all treatment lines. It is still controversial about the efficacy of Pmab for patients that had progressed on prior cetuximab (Cmab), though there had been a few reports (from Metges et al. and Wadlow et al.) regarding the efficacy of Pmab after Cmab refractory or intolerance. To evaluate the efficacy and safety of Pmab in patients with cetuximab-refractory mCRC, in comparison with anti-EGFR antibody naive patients (Cmab-naive) and Cmab-refractory or intolerance patients (prior-Cmab). Methods: Two hundred patients with mCRC treated by Pmab contained chemotherapy were retrospectively registered from 20 centers in Japan (HGCSG 1002 study). Of these, the patients that were refractory to or intolerant for 5-FU/ irinotecan/ oxaliplatin, and were administered Pmab monotherapy were included in this analysis. Results: Of 93 patients (44 prior-Cmab and 49 Cmab-naiv...