An effective low-dose mitomycin regimen for hormonal- and chemotherapy-refractory patients with metastatic breast cancer.

Ninety evaluable metastatic breast cancer patients refractory to hormonal therapy and combinations of cyclophosphamide, methotrexate, 5-fluorouracil, and doxorubicin were treated with a low-dose mitomycin regimen, i.e., 10 mg/m2 intravenously every 28 days. In order to minimize thrombocytopenia, dose de-escalations related to platelet counts were made. One patient (1%) had a complete response and 17% had partial responses for a median duration of 4 months. The time to progression for the responders and stabilized patients was similar; however, the responders and stabilized patients lived significantly longer than did the progressors. Hematologic toxicity was minimized because of planned de-escalations in mitomycin dosage. Perivenous ulceration, both immediate and delayed (8%), congestive heart failure (2%), and heart-renal failure with malignant hypertension (2%) resulted in significant morbidity, including two drug-related deaths. Although mitomycin dosages were successfully titrated according to platelet counts in this group of chemotherapy-refractory patients, prolonged use of this drug in adjuvant or early metastatic breast cancer patients is not recommended because of potentially irreversible thrombocytopenia.