Phase II study of combination chemotherapy with irinotecan and cetuximab for pretreated metastatic colorectal cancer harboring wild-type KRAS.

The aim of this study was to prospectively evaluate the efficacy of combination irinotecan and cetuximab chemotherapy in patients with pretreated metastatic colorectal cancer harboring wild-type KRAS. Patients with metastatic colorectal cancer that had progressed after chemotherapy with irinotecan, oxaliplatin, and fluoropyrimidine were included. KRAS status was evaluated using the Cycleave PCR method; only patients without KRAS mutations were included. Cetuximab was administered initially at 400 mg/m² followed by weekly 250 mg/m² infusions. Irinotecan was administered biweekly. From October 2008 to April 2009, a total of 30 patients were enrolled. The objective response rate was 30.0% (95% confidence interval [CI], 14.7-49.4%) and the disease control rate (complete response, partial response, or stable disease) was 80.0% (95% CI, 61.4-92.3%). Among the 15 patients with stable disease, 11 patients experienced >10% tumor shrinkage. Median progression-free survival was 5.8 months (95% CI, 4.1-7.6). Median overall survival was not reached at a median follow-up of 10.1 months. Grade 2 skin toxicity was observed in 23 patients, while no grade 3 skin toxicity was observed. Combined irinotecan and cetuximab is effective for pretreated metastatic wild-type KRAS colorectal cancer.