First-Line Vinorelbine-Mitoxantrone Combination in Metastatic Breast Cancer Patients Relapsing after an Adjuvant Anthracycline Regimen: Results of a Phase II Study

PURPOSE: Previous studies demonstrated that doxorubicin and vinorelbine combinations in first-line chemotherapy are highly active in metastatic breast cancer. Mitoxantrone is an anthracenedione with low cardiotoxicity, and seems to be effective when combined with vinorelbine after prior exposure to anthracyclines. PATIENTS AND METHODS: Seventy-two patients with metastatic breast cancer were included in a phase II study. All patients had previously received one anthracycline-containing regimen (doxorubicin or epirubicin) in an adjuvant setting. Vinorelbine was administered at 25 mg/m2 in a 20-min intravenous (i. v.) infusion, days 1 and 8. Mitoxantrone was given at 10 mg/m2 (66 patients) or 12 mg/m2 (6 patients) in a slow i.v. infusion on day 1. Courses were repeated every 3 weeks. RESULTS: Sixty-five patients were evaluable for response; the objective response rate was 49% (95% CI: 37-63%), including four complete and 28 partial responses, with a median duration of response of 7 months (range 2.3-27). Median overall survival was 19 months (range 2-48). Grade 3-4 granulocytopenia was observed in 46% of patients. There were 12 admissions (3% of cycles), involving 17% of patients for febrile neutropenia. Seven patients (10%) experienced grade 3 or 4 cardiotoxicity, and 1 patient died of cardiac heart failure. Other side effects were rare and mild. CONCLUSIONS: The vinorelbine and mitoxantrone combination is an active regimen with low toxic complications when cumulative doses of mitoxantrone are limited to 70 mg/m2. The results in this phase II study make it worthwhile including this regimen in a phase III study for patients who have previously received an anthracycline-containing regimen.