Should soybean agglutinin purging be performed in breast cancer patients undergoing autologous stem cell transplantation? A retrospective analysis of 48 patients.

High-dose chemotherapy (HDC) followed by autologous stem cell transplantation (ASCT) has gained an increasing role in the treatment of high-risk Stage II-III and/or metastatic breast cancer patients. Several investigators reported on a high rate of tumor cells contaminating the bone marrow and peripheral blood stem cell collection. Nevertheless, the clinical implication of reinfusion of tumor cells with the stem cells to the relapse rate is still uncertain. In this retrospective analysis we compare the outcome and the toxicity of 29 patients with high-risk Stage II-III and 19 metastatic breast cancer patients who underwent HDC with ASCT. Thirteen patients underwent transplant with soybean agglutinin (SBA)-purged graft, while 35 consecutive patients received unmanipulated graft. Engraftment was significantly faster for the nonpurged transplant. No differences in disease-free survival, freedom from relapse, or overall survival were noted in both groups during a median follow up time of 14 months. We conclude that tumor cell purging using SBA in breast cancer patients is not warranted. New purging methods are needed to assess the role of tumor cell purging in breast cancer patients.