Phase II study of biweekly irinotecan and mitomycin C combination therapy in patients with fluoropyrimidine-resistant advanced colorectal cancer

Purpose. Experimental studies have shown that mitomycin C (MMC) acts synergistically with irinotecan. We evaluated the antitumor activity and toxicity of a combination of irinotecan and MMC in patients with metastatic colorectal cancer resistant to fluoropyrimidines. Methods. Eligible patients had evidence of tumor progression while receiving fluoropyrimidine-based regimens or had disease recurrence within 6 months after the completion of adjuvant treatment with fluoropyrimidines. Irinotecan (150 mg/m(2)) and MMC (5 mg/m(2)) were administered on days 1 and 15 of a 28-day cycle. Treatment was repeated every 4 weeks. Results. Among the 41 patients enrolled, 37 (90%) had received previous chemotherapy for metastatic disease, and 4 had received adjuvant chemotherapy alone. Objective responses were observed in 14 patients (34%, 95% confidence interval 20-49%). The median time to progression was 4.2 months, and the median survival time was 11.9 months. The study treatment was well tolerated; the median number of cycles received was four. Grade 3 or 4 neutropenia, the most common toxic effect, occurred in 20 patients (49%). Grade 3 or 4 thrombocytopenia occurred in four patients (10%) and grade 3 diarrhea in one patient. Conclusions. Our results suggest that irinotecan and MMC combination therapy is effective and well tolerated in patients with fluoropyrimidine-resistant metastatic colorectal cancer. Further clinical investigation of this regimen is warranted.