Comparative analysis of engraftment after cryopreservation of peripheral blood stem cell autografts by controlled- versus uncontrolled-rate methods.

Peripheral blood stem/progenitor cells (PBSC) were cryopreserved by different methods and their clonogenic viabilities were compared. The traditional cryopreservation method involves controlled-rate freezing with 10% dimethyl sulfoxide (DMSO) and a programmed freezer (PF). The alternative method incorporates 6% hydroxyethyl starch and 5% DMSO without PF. In this non-randomized study, we analyzed the data of 24 patients (aged 1-17 years) who were in their first complete remission and who had undergone PBSC autograft (PBSCT) for high-risk acute lymphoblastic leukemia, to determine the effects of these two different methods of cryopreservation on time to engraftment and transfusion requirements after PBSCT. In all patients, PBSC were collected within 5 months of diagnosis and all had been conditioned with the high-dose MCVAC regimen (MCNU, cytosine arabinoside, etoposide and cyclophosphamide) without total body irradiation. Twelve patients received PBSC that had been cryopreserved by the uncontrolled method without PF and the data were compared by actuarial analysis to those of 12 historical controls whose cells had been frozen by PF. No difference was observed in the time to engraftment of granulocytes and platelets or the transfusion requirements between the two groups. Our results indicate that, in terms of preserving engraftment potential, the simplified uncontrolled-rate cryopreservation method is at least as effective as the traditional controlled-rate freezing procedure with PF.