EVALUATION OF MOBILIZED CD34-SCALE COLLECTION BY LEUKAPHERESIS( CELL COUNTS TO GUIDE TIMING AND YIELD OF LARGE)

We have previously reported a more than 50% risk of insufficient harve sts (<2 x 10(6) CD34+ cells/kg) following a fixed timing of leukaphere sis in an unselected patient population collected for autologous stem cell transplantation. The failures were easily identified as patients who had <20,000/ml CD34+ blood cells at the time of harvest. Consequen tly, in an attempt to optimize the timing strategy, we decided to perf orm daily analysis of the blood levels and perform leukapheresis withi n 24 h after the blood cell count exceeded 20,000 CD34+/ml. The result s of this prospective study showed (a) that leukapheresis collections that were initiated based on the CD34+ blood level resulted in a succe ss rate of 85% following 1-3 day harvests, (b) that high-level mobiliz ers with >80,000 CD34+ cells/ml can be harvested succesfully by only o ne procedure, and (c) that low-level mobilizers with <40,000 CD34+ cel ls/ml still have a high risk of inadequate harvests. In summary, the o ptimized timing strategy is effective, but there is still room for imp rovement. First, new potent priming procedures for low-level and bad m obilizers are required, and second, algorithms to reduce the leukapher esis volume and time for high-level mobilizers should be established.