Mitomycin C and vinblastine in combination with amifostine in metastatic breast cancer. A feasibility study of the EORTC--Investigational Drug Branch for Breast Cancer (IDBBC).

Mitomycin C (MMC)-vinblastine (VBL) is a regimen that has commonly been used as salvage therapy for advanced breast cancer for many years. The hematologic toxicity of this combination is one aspect that limits its usefulness. Amifostine, an organic thiophosphate, has been developed as a selective chemoprotective agent. In this pilot study, we tested the feasibility of MMC/VBL administration in combination with amifostine and we monitored the hematologic toxicity closely. Patients having failed one or two chemotherapy regimens for advanced breast cancer, with a good performance status scored at 2 or better and measurable or evaluable lesion(s), were eligible. They were treated according to the following schedule: mitomycin C 10 mg/m2 i.v. day 1, vinblastine 5 mg/m2 i.v. day 1 and 15, amifostine 910 mg/m2 in short i.v. infusion prior to MMC. Premedication consisted of dexamethasone 3 x 20 mg, haloperidol 2 x 0.5 mg p.o., hydration with 11 of normal saline, metoclopramide 1.5 mg/kg in short infusion and procyclide HCl 10 mg i.v. Cycles were repeated every 4 weeks. In all, 14 cycles were administrated to six heavily pretreated patients. Following the first cycle, five of the six patients experienced grade 3 or 4 neutropenia on day 15, and consequently did not receive the second vinblastine administration as planned. Three out of four patients receiving two or more cycles had moderate thrombocytopenia. There were no patients with neutropenic fever or major bleeding problems. The MMC/VBL+amifostine regimen was well tolerated regarding other toxicities. Neither amifostine-related acute vomiting nor any significant decrease in blood pressure was observed. Administration of amifostine in combination with MMC/VBL was feasible but in this group of heavily pretreated patients there were no hints of a protective effect of amifostine on the hematologic toxicity profile of this chemotherapy regimen.