The use of mitoxantrone, 5-fluorouracil and high-dose leucovorin in the treatment of advanced breast cancer

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Metastatic breast cancer remains an incurable disease; therefore, both the efficacy and the toxicity of palliative chemotherapy are important considerations. Mitoxantrone and 5-fluorouracil (5-FU) with high dose leucovorin are active drugs in the treatment of breast cancer, and both can be given with relatively few side effects. We evaluated the efficacy and toxicity of these agents in a combination regimen for the treatment of metastatic breast cancer. In a phase II study, we treated 35 women with metastatic breast cancer with the following regimen: mitoxantrone 12 mg/m2 i.v. day 1; leucovorin 300 mg i.v. over 1 hour followed by 5-FU 350 mg/m2 i.v. push on days 1, 2 and 3; courses repeated every 21 days. Responding patients received a total of 6-8 courses. Most patients were receiving second-line chemotherapy for metastatic breast cancer, but some were receiving first-line therapy following failure of adjuvant chemotherapy. Twenty of 31 assessable patients (65%) had objective responses; in addition, 2 of 4 patients with bone-only metastases had sustained symptomatic responses. Toxicity was mild and the regimen was well tolerated. The activity of this drug combination has been verified in several other phase II studies. The combination of mitoxantrone, 5-FU and high-dose leucovorin provides an attractive option for second-line chemotherapy of metastatic breast cancer. The efficacy of this combination in first-line therapy is currently being compared to cyclophosphamide, methotrexate and 5-FU (CMF) in a randomized trial.