Five‐day continuous‐infusion vinblastine in the treatment of breast cancer

One hundred six evaluable patients with metastatic breast cancer refractory to prior chemotherapy were treated with 5‐day intravenous infusions of vinblastine at 1.4 to 2.0 mg/m²/day, through silastic elastomer permanent central venous catheters. Thirty‐nine patients achieved objective responses; 5 were considered complete. The overall response rate of 37% was independent of prior exposure to intermittent intravenous vinca alkaloids or prior response to front‐line doxorubicin combination chemotherapy. Objective responses were documented in 48% of the patients who received daily doses above 1.7 mg/m² and in 32% and 29% of those treated with 1.7 mg/m² or less, respectively (P = 0.10). Myelosuppression was more severe in responders, who received higher average doses, (median average nadir, 850 granulocytes/mm³) than in nonresponders (median, 1300 granulocytes/mm³), but was always rapidly reversible. Infections related to neutropenia were uncommon. Catheter‐related toxicities occurred in 13 of 106 patients. Other toxicities were limited. These results confirm that vinblastine given as a continuous 5‐day infusion is one of the most effective agents in the treatment of metastatic breast cancer and suggest that its activity is dose‐dependent.