Phase II pilot study of high-dose busulfan and CY followed by autologous BM or peripheral blood stem cell transplantation in patients with advanced chemosensitive breast cancer.

The combination of busulfan and CY ('BU-CY') has been widely employed as a conditioning regimen for patients undergoing BMT for hematologic malignancies. However, little information is available regarding the utility of BU-CY in treating patients with advanced breast cancer. Fifteen patients with heavily pretreated Stage IIIB or Stage IV chemosensitive breast cancer were treated with busulfan (16 mg/kg) and CY (6000 mg/m2) followed by rescue with autologous BM or autologous peripheral blood stem cells. Toxicity and engraftment parameters were similar to those observed in patients receiving BU-CY for other indications. The overall response rate was 87%, with 53% of patients achieving CR. The median progression-free survival was 164 days, and the median overall survival was 292 days. We conclude that BU-CY is able to induce remissions in a high percentage of patients with heavily pretreated advanced breast cancer. However, remissions are brief, and alternative strategies for patient selection and/or management will be necessary to improve on these results.