Mitomycin C and vinblastine in anthracycline-resistant metastatic breast cancer: a phase II study.

The purpose of this phase II study was to evaluate the clinical efficacy of mitomycin C and vinblastine in patients with anthracycline-resistant metastatic breast cancer. This single-center, non-randomized trial enrolled 39 patients. Eligible patients must have received at least three chemotherapy regimens with epirubicin or CAF and had treatment failure while on chemotherapy or within 6 months of completing therapy. Treatment consisted of mitomycin C at a starting dose of 8 mg/m2 on day 1 and vinblastine (8 mg/m2, days 1 and 28). The regimen was repeated every 6 weeks with a 20% dose escalation of both drugs after the first cycle in the absence of grade III hematologic or other toxicity. On an intent-to-treat basis, 38 patients were eligible for assessment; 9 (23.7%, 95% confidence interval 1.92-2.45%) achieved a partial response and 13 (34.2%) had stable disease. The median time to disease progression was 6.21+/-4.26 months (range, 1-15; 95% confidence interval, 4.81-7.61), and the median survival was 10.76+/-7.6 (range, 1-29; 95% confidence interval 8.0-13.1%). Responsive patients had a significantly better survival than those with stable and progressive disease. Treatment was well tolerated. Anemia and neutropenia (grade I-III) developed in 28.9% and 26.3% of the patients, respectively. One patient with grade III granulocytopenia developed fever and infection that required hospitalization. Moderate neurotoxicity, myalgia, constipation, diarrhea and alopecia were observed. No toxic death occurred. Mitomycin C plus vinblastine is an effective and well-tolerated regimen for anthracycline resistant cancer.