Phase I/II trial of high dose mitoxantrone in metastatic breast cancer: The M.D. Anderson Cancer Center experience

Anthracyclines are among the most active agents in metastatic breast cancer. Mitoxantrone demonstrated a different toxicity profile when compared to doxorubicin. We performed a phase I/II study of single-agent high-dose mitoxantrone therapy for advanced breast cancer. Nineteen patients who had a diagnosis of metastatic breast cancer received treatment at the M.D. Anderson Cancer Center between June 1986 and December 1987. The patients received escalating doses of mitoxantrone until a maximum tolerated dose (MTD), defined as grade 3 or 4 nonhematologic toxicity or infection, was obtained. The starting dose of 25 mg/m², given by short intravenous infusion, was escalated by 25% in each five-patient cohort if each patient in the previous cohort tolerated the initial course and 2 or fewer patients reached the MTD. The median cumulative dose of mitoxantrone was 93 mg/m² (range, 25-205) and the maximum single dose was 39 mg/m². Myelosuppression was the dose limiting toxicity. The median duration of granulocyte count ≤ 250/μl was 5-7 days. Four patients (22%) had infections that required hospitalization, 3 patients (17%) had cardiac toxicity. One patient (6%) achieved a complete response, and 3 (17%) had a partial response, with an overall response rate of 22.3%. No apparent dose-response relationship was observed in our study. The mitoxantrone dosage recommended for phase II studies is 25 mg/m² every 3-4 weeks. We conclude that high-dose mitoxantrone therapy for metastatic breast cancer was relatively well tolerated but was not associated with a higher response rate than that of standard dose mitoxantrone.