Randomized phase II study of irinotecan plus mitomycin C vs. oxaliplatin plus mitomycin C in patients with advanced fluoropyrimidine/leucovorin-pretreated colorectal cancer.

INTRODUCTION: Irinotecan and oxaliplatin are two new agents with promising activity in advanced colorectal cancer. Based on preclinical and clinical evidence that both drugs might act synergistically with mitomycin C, a randomized study using a 'pick the winner' design was undertaken to determine the effectiveness and tolerance of these two combination schedules in patients with fluoropyrimidine/leucovorin-pretreated advanced colorectal cancer. PATIENTS AND METHODS: Sixty-four patients with metastatic colorectal cancer, who progressed while receiving or within 6 months after discontinuing palliative chemotherapy with fluoropyrimidines/leucovorin were enrolled onto this study. They were randomly assigned to treatment with irinotecan 120 mg/m2 on days 1 + 15 plus mitomycin C 8 mg/m2 on day 1 (arm A) or oxaliplatin 85 mg/M2 on days 1 + 15 plus mitomycin C 8 mg/m2 on day 1 (arm B). In both treatment arms, courses were repeated every 4 weeks. RESULTS: The objective response rate in arm A is 7/33 (21.2%; 95% confidence interval, 9.0-38.9%) as compared to 5/31 in arm B (16.1%; 95% CI, 5.5-34.7%). Stable disease was noted in 48.5 vs. 45.2%, whereas the tumor progressed in 30.3 vs. 38.7%, respectively. Similar to the recorded response activities, the difference of the two combination regimens in terms of median time to progression (7.0 vs. 5.2 months) and overall survival (12.0 vs. 11.2 months) was only minor and clincally insignificant. The tolerance of treatment was acceptable in both arms, though severe adverse reactions requiring dose reductions (30 vs. 16%) and treatment delays (22 vs. 13% of courses) were more commonly noted with irinotecan/mitomycin C. The most common toxicities in arm A were neutropenia (85%; WHO grade 3/4 in 33%), thrombocytopenia (52%), diarrhea (45%), emesis (52%) and alopecia (92%). In arm B, common toxicities included neutropenia (68%; grade 3/4 in 13%), thrombocytopenia (81%), emesis (52%), and peripheral neutropathy (48%). CONCLUSIONS: Both mitomycin C combination regimens seem to provide an acceptable therapeutic index in patients with fluoropyrimidine/leucovorin-pretreated metastatic colorectal cancer. In view of the increasing need for a broader chemotherapeutic armentarium for second-line therapy of this common malignant disease, both regimens may be worthwhile to undergo further clinical investigation.