Vinblastine given as a continuous 5-day infusion in the treatment of refractory advanced breast cancer

In an attempt to improve the therapeutic index of vinblastine by maintaining a prolonged, constant plasma level, it was given as a continuous 5-day infusion at 1.4-2.0 mg/m2/day. Among the 30 evaluable patients with advanced refractory breast cancer who had been extensively treated previously, there were one complete and 11 partial responders, with an overall response rate of 40%. Six of the 12 patients who had previously received a conventional dose schedule of vinca alkaloids responded, including two who had progressed with intermittent bolus iv injections of vinblastine. Responses were seen in all organ sites of involvement, with durations of 2-8+ months (median, 6). Myelosuppression was mild to moderate at doses of between 1.4 and 1.8 mg/m2/day but became severe at 2 mg/m2, with leukopenia (wbcs, < 2000/mm3) and granulocytopenia (absolute granulocytes, < 1000/mm3) occurring in 75% of administered courses. Other toxic effects were infrequent and acceptable. Our results suggest that vinblastine given as a continuous 5-day infusion is highly effective in the treatment of patients with advanced metastatic breast cancer, including a few whose disease was felt to be resistant to a conventional dose schedule of vinca alkaloids.