Simultaneous Double-Purging of Breast Cancer Cells from Leukapheresis Products by Immunomagnetic CD34+ Cell Enrichment and Tumor Cell Depletion

During the last few years breast cancer has become an important field for peripheral blood progenitor cell 3transplantation (PBPCT) following high dose (HD) chemotherapy [2]. The high prognostic value of bone marrow micrometastasis and the mobilization of malignant cells into the peripheral blood following priming for PBPC collection are well known [5,7,18]. Although the negative influence of tumor cells contaminating autografts on the clinical outcome after stem cell retransfusion is still not proven by prospective clinical studies, the reduction of residual tumor cells is a main target of leukapheresis product (LP) processing. Immunomagnetic CD34+ cell enrichment (Baxter Isolex 300i system) is a widely applied purging procedure (+ selection) [13]. An additional second immunomagnetic purging (− selection) step can increase the tumor cell depletion [3,14]. We applied a new simultaneous +/- immunomagnetic purging method in an experimental setting and in clinical samples. Additionally, we compared the results with our own clinical data from patients who underwent stem cell rescue with PBPC samples purged by CD34+ selection only or toxic lipid (ET-18-OCH3) incubation.