Chemotherapy with mitoxantrone in combination with continuous infusion vinblastine for metastatic breast cancer

The efficacy of mitoxantrone in combination with vinblastine was assessed in 156 patients with metastatic breast cancer who had been treated previously with one or multiple chemotherapeutic regimens. Mitoxantrone was given by random assignment, either as a 10 mg/m2 single intravenous dose or in five consecutive daily fractions of 2 mg¿2. Vinblastine was given as a continuous intravenous infusion of 1.2 mg/m2 daily for 5 days. In 115 evaluable patients previously treated with doxorubicin, 21 objective responses (18%) and 11 minor responses (10%) were observed with similar distribution in the two treatment groups. Median time to progression was 27 weeks and 23 weeks, respectively. Eight (32%) of 25 patients who had not received doxorubicin achieved objective remissions and two (8%) had minor responses. Toxic effects were similar for the two treatment schedules. Major toxicities were myelosuppression and neutropenic fever. Other toxicities were mild. Cardiotoxicity, presumably caused by mitoxantrone, occurred in four patients. The combination of mitoxantrone and vinblastine appeared to offer no advantage over single-agent therapy, probably because of the dosage reduction required by the overlapping myelosuppressive toxicity.