INCREASED SENSITIVITY FOR DETECTION OF MICROMETASTASES IN BONE-MARROWPERIPHERAL-BLOOD STEM-CELL PRODUCTS FROM BREAST-CANCER PATIENTS BY NEGATIVE IMMUNOMAGNETIC SEPARATION/

Immunocytochemical detection (ICC) of isolated turner cells in bone ma rrow (BM) is currently the most established method for monitoring earl y dissemination in epithelial cancer. However, the low sample size tha t can practically be analyzed restricts the sensitivity and reliabilit y of the ICC method. To be able to analyze larger samples, a negative immunomagnetic separation (IMS) technique, utilising anti-CD45-conjuga ted Dynabeads, has been developed, Tumor-cell enrichment by depletion of CD45-expressing mononuclear cells (MNC) is followed by ICC for dete ction of the cytokeratin (CK)-positive (+) epithelial cells. In this s tudy, bone-marrow samples (n=165) and peripheral-blood-pro-genitor-cel l (PBPC) apheresis products (n = 22) from breast-cancer patients were analyzed. The negative IMS analysis of I to 2 X 10(7) MNC Was compared with ICC analysis of 2 x 10(6) unseparated MNC, Negative IMS resulted in 85% mean depletion of MNC, The results showed that 11.7% of the sa mples were positive by ICC analysis of unseparated MNC, as compared wi th 23.5% after negative IMS. In samples presenting > 10 CK+ cells, a 4 -fold higher number of positive cells was detected by the negative IMS technique. Moreover, there was no evidence for general enrichment of false-positive cells. Altogether our results show that negative IMS is an efficient enrichment method for sensitive detection of CK+ cells i n BM/PBPC products from breast-cancer patients. This opens the possibi lity for further characterization of micrometastatic tumor cells. (C) 1998 Wiley-Liss, Inc.