Chemotherapy with mitomycin C and vinblastine in pretreated metastatic breast cancer

In February 1986 we began a study to test the activity of mitomycin C (12 mg/m2) plus vinblastine (6 mg/m2) on day 1 of a 28-day cycle (MV) as second or third-line chemotherapy for metastatic breast cancer patients.

As of February 1988 the study was stopped after 26 patients had been enrolled. The median age of the patients was 54 years (range 35-78); all patients were progressive from chemotherapy; 15 (57.7%) patients were treated as second and 11 (42.3%) as third line; 19 (73.1%) patients had received anthracyclines as first (13 patients) or second-line (6 patients) chemotherapy; 18 (69.2%) patients had visceral involvement; 7 (26.9%) had one metastatic site, 11 (42.3%) two sites, 6 (23.1%) three sites and 2 (7.7%) four sites.

Overall, 86 cycles were administered, with a median number of 3 cycles per patient. Toxicity was mild; hematologic side effects required discontinuation of treatment in 3 cases. Vomiting occurred in 3 (11.5%) patients, nausea in 5 (19.2%). Moderate neurologic toxicity was recorded in 6 (23%) patients. No complete and 3 partial responses were observed. The objective response rate was 11.5% (exact 95% confidence interval, 2.4-30.1). Responses occurred independently of disease-free interval, dominant metastatic site, response to previous chemotherapy, previous anthracycline and line of treatment; all responses were recorded in patients under 50 years of age. Kaplan-Meier estimated median time to progression and overall survival were 13 and 40 weeks, respectively.

The MV regimen was well tolerated but showed little activity in pretreated metastatic breast cancer.