Mitoxantrone: an active new agent in the treatment of advanced breast cancer.

Sixty-five patients with advanced breast carcinoma were treated with mitoxantrone, an anthracenedione with structural similarities to adriamycin. The series included 26 patients who had received no prior chemotherapy. Treatment was given in a dose of 12-14 mg/m2 by IV infusion, repeated every 3 weeks. Sixty-two patients were evaluable for response, but all were evaluable for toxicity. One (2%) achieved a complete response and 18 (29%) a partial response (overall response rate 31%). The response rate in patients who had received no prior chemotherapy was 35%, vs 22% in previously treated patients. The median duration of response was 10 months (range 3.5-18.5 months). Two responders had previously failed to respond to adriamycin, and a third responder subsequently failed to respond to adriamycin. Neutropenia was the most frequently seen toxicity, with a WBC of less than 2,000/mm3 seen in 26 patients (40%), eight of whom (12%) had a neutropenic infection. Thrombocytopenia (less than 100,000/mm3) occurred in 12 patients (18%), but in three of these only after at least 6 months of treatment. Two patients developed readily reversible cardiac failure after prolonged treatment (11-13 months). Other toxicities were in general mild, and the drug was well tolerated: severe alopecia occurred in only one patient. Mitoxantrone is an active well-tolerated agent in the treatment of advanced breast carcinoma, but the risk of neutropenia requires careful supervision. The long-term risk of cardiotoxicity cannot yet be fully assessed.