Autografting with CD34(+) peripheral blood stem cells: retained engraftment capability and reduced tumour cell content

The efficacy of an immunomagnetic purging method and the Isolex 300 devices were assessed for selecting CD34(+) cells from leukapheresis products of 2 9 patients with non-Hodgkin's lymphoma (NHL), 39 with multiple myeloma and 33 with breast cancer. The mean purity of the CD34(+) cell population was 9 3.6% and the mean recovery was 67.7%. Following enzymatic cleavage by chymo papain the expression of Thy-1 and Leu-8 was significantly reduced without affecting haematological recovery. The population of selected CD34(+) cells of 4/8 patients with follicular lymphoma became PCR-negative. A 2.5 log re duction of tumour cells could be achieved in four patients with multiple my eloma as shown by a quantitative PCR assay. There were no tumour cells dete ctable in any of the 19 CD34(+) cell preparations of patients with breast c ancer. In 64 patients who received 94 cycles of high-dose therapy a mean nu mber of 4.7 x 10(6) CD34(+) cells/kg were autografted. The time needed for platelet reconstitution was different when a comparison was made with 156 p atients. who had received unmanipulated leukapheresis products (10 v 12 d, P = 0.006). No significant differences with regard to neutrophil recovery w ere noted. Five patients had a graft failure. Two of them died (on day 78 a nd 88 following PBSCT), and three patients were rescued with unmanipulated back-up transplants. In conclusion, the immunomagnetic selection of CD34(+) cells provides autografts with reduced tumour cell content and an engraftm ent ability similar to that of unmanipulated autografts.