A comparative trial of mitoxantrone and doxorubicin in patients with minimally pretreated breast cancer.

A randomized trial began in 1980 comparing the efficacy and toxicity of mitoxantrone and doxorubicin. Patients with metastatic breast cancer unresponsive to cyclophosphamide-methotrexate-5-fluorouracil with or without tamoxifen were randomized to either mitoxantrone, 12 mg/m2, or doxorubicin, 60 mg/m2, every 3 weeks. Patients were crossed over to the alternative treatment if they progressed after two courses or fail to respond after four courses. Fifty-nine patients have been randomized at the present time, and most of these have a performance status near to normal. During initial therapy, partial responses were obtained in 10 of 25 patients receiving doxorubicin, and a further 12 showed stable disease; 3 showed progressive disease. Of the 26 patients who received mitoxantrone as initial therapy, 7 achieved a partial response, 14 had stable disease, and 5 progressive disease. Twenty-seven patients received doxorubicin or mitoxantrone as secondary therapy; two patients each responded to these drugs, suggesting a lack of cross-resistance. The median time to response was 48 days for doxorubicin and 57 days for mitoxantrone. The duration of partial responses measured from the onset of response was similar for both drugs, being 84 days for doxorubicin and 96 days for mitoxantrone. Hematologic toxicity, vomiting, alopecia, and fatigue tended to be less frequent and less severe with mitoxantrone than with doxorubicin. Mitoxantrone appears to be an effective and well-tolerated agent for breast cancer. Definitive comparisons will be available at the completion of this study.