Phase II study of combination chemotherapy with biweekly cetuximab and irinotecan for wild-type KRAS metastatic colorectal cancer refractory to irinotecan, oxaliplatin, and fluoropyrimidines.

561 Background: Weekly cetuximab and irinotecan is a standard regimen in heavily pretreated patients with metastatic colorectal cancer (MCRC). The aim of this study was to prospectively evaluate the efficacy of combination chemotherapy with biweekly cetuximab and irinotecan in patients with pretreated MCRC harboring wild-type KRAS. Methods: Patients with wild- type KRAS MCRC that had progressed after chemotherapy with irinotecan, oxaliplatin, and fluoropyrimidine were included in this study. Cetuximab was administered at 500 mg/m2 biweekly with irinotecan. The primary endpoint was response rate. The secondary endpoints included adverse events, progression-free survival, and overall survival. The pharmacokinetics of cetuximab was also evaluated in five patients. Results: From May, 2009 to February, 2010, a total of 31 patients were enrolled from five institutions. One patient was not eligible. Among the 30 assessable patients, ECOG PS was 0 in 12, 1 in 16, and 2 in two patients. The objective response rate...