AIM: Cetuximab improves the prognosis for wild-type KRAS metastatic colorectal cancer (MCRC). We evaluated the safety and efficacy of cetuximab in combination with irinotecan in Japanese patients with wild-type KRAS MCRC refractory to irinotecan, oxaliplatin and fluoropyrimidines. METHODS: Cetuximab was administered initially at a dose of 400 mg/m2 , followed by weekly infusions at 250 mg/m2 . Irinotecan was administered every 2 weeks at 150 mg/m2 . Primary endpoint was the incidence of grade 3/4 adverse events; secondary endpoints included overall survival (OS), progression-free survival (PFS), response rate (RR), time to treatment failure (TTF), and TTF for irinotecan. RESULTS: Thirty-four patients were enrolled. Grade 3 or 4 toxicities were leucopenia (11.8%), neutropenia (23.5%), anemia (11.8%), fatigue (2.9%), anorexia (2.9%), diarrhea (14.7%) and hypomagnesemia (5.9%). Skin toxicities were as follows (any grade/grade 3): acne (94.2/8.8%), rash (55.9/0%), nail changes (75.5/8.8%) and hand-foot syndrome (55.9/5.9%). Median PFS was 6.0 months (95%CI; 4.7-7.4). Median OS was 12.9 months (95%CI; 10.0-15.9). RR was 26.4%. Median TTF was 5.1 months and median TTF for irinotecan was 5.0 months (95%CI; 4.3-5.6). CONCLUSION: Cetuximab with irinotecan therapy was well tolerated in Japanese patients with wild-type KRAS colorectal cancer refractory to irinotecan, oxaliplatin and fluoropyrimidine, thus demonstrating the feasibility of their usage.