Negative immunomagnetic purging of peripheral blood stem cell harvests from breast carcinoma patients reduces tumor cell contamination while not affecting hematopoietic recovery

BACKGROUND. Because tumor contamination of hematopoietic stern cell grafts may influence the outcome in breast carcinoma (BC) patients undergoing high dose chemotherapy (HDC), several ex vivo procedures for the purging of aut ologous harvests have been investigated. The authors studied the presence o f epithelial tumor cells and the growth of hematopoietic progenitors in per ipheral blood stem cell (PBSC) collections from patients with metastatic br east carcinoma before and after a purging procedure performed by a negative immunomagnetic BC cell separation. METHODS. Eighteen patients entered the study. Tumor contamination was asses sed by conventional immunocytochemistry (ICC) and by a liquid culture assay developed in the study laboratory. Committed and more primitive hematopoie tic progenitors were quantitated before and after the negative selection. T en patients received HDC with purged PBSC support. RESULTS. Before purging, 4 of 18 PBSC collections were found to be contamin ated by liquid culture; among these samples, only 1 was positive by ICC. Th ree of the four positive collections, including the ICC positive sample, be came negative after immunomagnetic selection whereas BC cells still were pr esent after the procedure in one harvest. A high recovery of both primitive and mature hematopoietic progenitors was found after the purging procedure . Patients receiving purged PBSC after myeloablation had a prompt and compl ete hematopoietic reconstitution, and no graft failure was observed at a me dian follow-up of 1 year. CONCLUSIONS. The preliminary results of the current study suggest that nega tive selection of BC cells is able to purge PBSC effectively while having n o apparent affect on hematopoietic progenitor recovery in vitro and in vivo . (C) 2000 American Cancer Society.