MONITORING OF TUMOR-CELL PURGING AFTER HIGHLY EFFICIENT IMMUNOMAGNETIC SELECTION OF CD34 CELLS FROM LEUKAPHERESIS PRODUCTS IN BREAST-CANCERPATIENTS - COMPARISON OF IMMUNOCYTOCHEMICAL TUMOR-CELL STAINING AND REVERSE TRANSCRIPTASE-POLYMERASE CHAIN-REACTION

We studied the efficiency of indirect tumor cell purging via enrichmen t of CD34(+) hematopoietic progenitor cells from leukapheresis product s (LP) in breast cancer patients based on immunomagnetic selection of CD34(+) cells. Detection of tumor cells was made by immunocytochemical staining. In addition, we evaluated the capacity of cytokeratin 19 (C K19)-and a novel epidermal growth factor receptor (EGF-R)-specific rev erse transcriptase-polymerase chain reaction (RT-PCR) for monitoring t umor cell depletion. LP from 13 breast cancer patients were analyzed. Twenty-three CD34 selection procedures were performed. A median of 1.4 x 10(10) total nucleated cells ([TNC] range, 0.88 to 3.5 x 10(10)) wi th a median CD34 purity of 2.5% (range, 0.4% to 6.3%) were entered int o the selection procedure. Immunomagnetic CD34 enrichment resulted in a median purity of 83.3% (range, 45% to 95.4%) and a median recovery o f 73.2% (range, 22% to 95%). Retransfusion of CD34-selected cells afte r high-dose chemotherapy resulted in a rapid and sustained hematologic recovery, reaching an absolute neutrophil count of 500/mu L at day +1 0 and platelet count of 20,000/mu L at day +11. Tumor cell depletion w as quantified by immunocytochemical detection of CK19-positive cells. By this method, a median tumor cell depletion of 1.9 log (range, 0.7 t o >3 log) could be demonstrated. Immunocytochemical detection of tumor cells was more sensitive than RT-PCR, yielding positive results in 87 % of LP (17 to 21) versus 58% positive LP (10 of 17). However, EGF-R-b ased RT-PCR was much more sensitive than CK19-based RT-PCR (10 of 17 v 1 of 17). Despite highly efficient CD34 selection, tumor cells were s till detectable after CD34 enrichment using immunocytochemistry and EG F-R-specific RT-PCR. Thus, this novel EGF-R-specific RT-PCR appears to be of value as an additional method to detect contaminating breast ca ncer cells within LP. (C) 1997 by The American Society of Hematology.