Mitomycin: its evolving role in the treatment of breast cancer.

Investigators have compiled extensive experience with mitomycin in the treatment of patients with breast cancer. Given as a single agent in intermittent schedules, mitomycin has induced responses of 26-38% in previously untreated patients and of 15-25% in those exposed to multiple prior chemotherapy regimens. Duration of response has been short. Toxicity, primarily myelosuppression, is largely dose-dependent. The dose-dependent efficacy of mitomycin has not yet been addressed. Preclinical studies suggest that optimal single-agent results are obtained when mitomycin is given in intermittent, high-dose schedules. Combination chemotherapy with mitomycin has proven more effective than single-agent therapy. Mitomycin given in combination with doxorubicin produces higher response rates than have been obtained with mitomycin alone. The 3M combination (mitomycin/mitoxantrone/methotrexate) appears effective and well tolerated at the doses described. Future research should focus on the development of polychemotherapeutic regimens that can be delivered in sequential or alternating schedules. Such regimens may yield quicker responses, and thus improve survival, in patients with breast cancer.