Short-term chemotherapy of poor-prognosis metastatic breast cancer with three non-cross resistant chemotherapy regimens. A Southwest Oncology Group Study.

A Southwest Oncology Group pilot study was designed to evaluate a brief, 4.5-month induction course of chemotherapy with three presumably non-cross resistant regimens in poor-prognosis metastatic breast cancer. Sixty-three patients were treated with doxorubicin, cyclophosphamide, plus vincristine on day 1, methotrexate followed 30 minutes later by 5-fluorouracil (5-FU) on day 22, and mitomycin C plus 3 days of vinblastine on day 43. All three sequential regimens were repeated once and therapy was then discontinued in responding patients. The same chemotherapy was reinstituted at the time of relapse. The overall response rate to the induction chemotherapy was 35% and included only one complete response (2%). Median response duration was 9 months. Respondents were off all therapy for a median of 5 months (range, 1-12+ months) and were followed without evidence of progressive disease. Response to retreatment was 30% with no complete responses seen. Overall median survival from the data of diagnosis of metastatic disease was 24 months, with a median survival of 14 months from the date of initiation of therapy. Toxicity for this induction regimen was moderate with two treatment-related deaths secondary to myelosuppression. While the results of this pilot study fail to support the use of non-cross resistant regimens in breast cancer, short-term therapy appears to have no adverse effect on survival and resulted in significant periods during which no therapy was given, resulting in a reduction in overall toxicity.