Two novel high-dose treatment regimens for metastatic breast cancer--ifosfamide, carboplatin, plus etoposide and mitoxantrone plus thiotepa: outcomes and toxicities.

This report describes the results of two phase I/II dose escalation trials for the treatment of metastatic breast cancer. Successive groups of patients with metastatic breast cancer responsive to induction therapy following standard doses of chemotherapy were treated with escalating doses of ifosfamide (6,000 to 24,000 mg/m2), carboplatin (1,200 to 2,100 mg/m2), and etoposide (1,800 to 3,000 mg/m2) followed by autologous stem cell rescue. The maximum tolerated doses of these drugs were defined as ifosfamide 20,100 mg/m2, carboplatin 1,800 mg/m2, and etoposide 3,000 mg/m2. Major nonhematologic toxicity consisted of mucositis and enteritis, and the dose-limiting toxicities were central nervous system toxicity and acute renal failure. The overall treatment-related mortality rate was 4%. The event-free survival rate at 500 days for these patients was 31%. Patients with metastatic breast cancer refractory to all standard dose therapy were treated with escalating doses of mitoxantrone (45 to 105 mg/m2) and thiotepa (900 to 1,350 mg/m2) followed by autologous stem cell rescue. The maximum tolerated doses of these drugs were defined as mitoxantrone 90 mg/m2 and thiotepa 1,200 mg/m2 with mucositis and enteritis as the major nonhematologic toxicities and delayed myelosuppression as the dose-limiting toxicity. Twelve percent of the patients remain event free at 500 days and the treatment-related mortality rate for this group of heavily pretreated patients was 17%. These data suggest that patients with metastatic breast cancer may benefit from high-dose therapy and that treatment-related toxicity is tolerable.