Prolonged disease control by nonmyeloablative allogeneic transplantation for metastatic breast cancer

We found earlier that high-dose chemotherapy with Allo-SCT produced a tumor response in patients with chemorefractory metastatic breast cancer. In this study, we examined the efficacy and toxicity of nonmyeloablative allogeneic PBSC transplantation in patients with chemosensitive metastatic breast cancer. Twelve patients with metastatic breast carcinoma who had stable disease after standard-dose chemotherapy and six who had a partial response underwent allogeneic transplantation. The conditioning regimen consisted of reduced-intensity fludarabine and melphalan. All patients achieved engraftment and hematopoietic recovery. Nine patients developed grade II or higher acute GVHD; seven of these nine responded to immunosuppressive therapy. Fourteen patients developed chronic GVHD. The treatment-related mortality rate was 11%. With a median follow-up of 565 days, the median survival duration was 643 days and the median progression-free survival duration was 202 days. Two patients are alive with a complete response 1555 and 2526 days after SCT, and one patient is alive with progressive bone disease at day 1118. We conclude that among patients with chemotherapy-sensitive metastatic breast cancer, a fraction will achieve a durable complete response after SCT with a reduced-intensity conditioning regimen. The question remains how to improve the overall efficacy and reduce the mortality rate for this approach.