A phase II study of chlorozotocin in advanced large bowel carcinoma. A cooperative study between two institutions.

Mayo clinic and georgetown university carried out a cooperative phase II study of chlorozotocin in measurable advanced large bowel carcinoma. Of 78 evaluable patients randomized, 39 received low-dose (120 mg/m2 if previously untreated, 100 mg/m2 if previously treated) and 39 high-dose (200 mg/m2 if previously untreated, 175 mg/m2 if previously treated) chlorozotocin intravenously at 6-week intervals. Both groups were comparable in regard to age, prior treatment, treating institution, site of metastases, and performance scores. Overall response rate was 8%, including 5% in low-dose patients and 10% in high-dose patients. Toxicity was mild to moderate, with gastrointestinal toxicity substantially, and hematologic toxicity somewhat less, than seen with other nitrosoureas. Time to progression and survival showed no significant difference between patients treated on the low- and high-dose schedules. As chlorozotocin produced less nausea and vomiting than other nitrosoureas, even in the high-dose regimen, it should be considered for evaluation in neoplasms where nitrosoureas have shown more activity than in colorectal carcinoma.