High-dose mitoxantrone and cyclophosphamide without stem cell support in patients with high-risk and advanced breast...

Currently employed high-dose regimens for patients with breast carcinoma consist mainly of single-cycle combinations of alkylating agents. In a previous Phase I trial, the authors developed a tandem high-dose combination of two cycles of mitoxantrone and cyclophosphamide for the treatment of patients with metastatic breast carcinoma (MBC) and high-risk breast carcinoma (HRBC). Treatment was delivered with granulocyte-colony stimulating factor (G-CSF) but without stem cell support to avoid potential tumor cell reinfusion. The objective was to validate the safety and obtain preliminary efficacy assessment of this combination in a Phase II trial.

Fifty-three patients were included: 27 patients with MBC and 26 patients with HRBC. After standard induction treatment, patients received two cycles of mitoxantrone 25 mg/m2 and cyclophosphamide 4000 mg/m2 separated by a 4-week interval. Patients received G-CSF and ciprofloxacin until hematologic recovery. Follow-up was performed in an outpatient setting.

One hundred one of 106 projected cycles (95%) were delivered. The mean dose intensities achieved were mitoxantrone 5.8 mg/m2 per week and cyclophosphamide 933 mg/m2 per week. Infection developed in 46% of the cycles, and platelet transfusions were required in 42%. Nonhematologic toxicity was mainly Grade 3 emesis. There were no toxic deaths. In 17 evaluable patients with MBC, 13 patients (77%) had response improvements, including 7 complete responses (41%).

Treatment with two cycles of mitoxantrone 25 mg/m2 and cyclophosphamide 4000 mg/m2 with G-CSF but without stem cell support was well tolerated. The dose intensities achieved approach those obtained with conventional high-dose therapy. This combination warrants further investigation as an alternative to conventional high-dose regimens.