Outcome of 51 autologous peripheral blood stem cell transplants after uncontrolled-rate freezing ("dump freezing") using -80°C mechanical freezer.

BACKGROUND AND OBJECTIVE: Controlled-rate freezing is a complicated, expensive, and time-consuming procedure. Therefore, there is a growing interest in uncontrolled-rate freezing (UCF) with -80°C mechanical freezers for cryopreservation of hematopoietic stem cells. This is a retrospective analysis of efficiency of UCF and outcome of autologous peripheral hematopoietic stem cell (PBSC) transplants at our center from December 2011 to June 2016.

MATERIALS AND METHODS: Cryoprotectant solutions used included 5% dimethyl sulfoxide and 5% albumin with 2% hydroxyethyl starch and stored at -80°C mechanical freezer till transplant. Evaluation of cryopreservation was studied by analyzing the variation in cellularity, viability, and CD34+ stem cell dose recovery as well as clinical follow-up with engraftment.

RESULTS: A total of 51 patients (23 females and 28 males) underwent autologous PBSC transplantations with a median age of 31 years (range: 3-60 years) for both hematological and nonhematological indications. Mean recovery post by UCF at -80°C mechanical was 92.9% ± 15.5% for nucleated cells, 86.6% ± 15.5% for viability, and 80% ± 21.5% in CD34+ dose. The median day to neutrophil engraftment was 10 (range 5-14 days) and platelets engraftment was 15 (range 8-45 days). The cryopreserved products were stored at -80°C for median 7 days (range 2-41 day) before transplant.

DISCUSSION/CONCLUSION: Our analysis shows that PBSC can be successfully cryopreserved with mechanical uncontrolled rate freezing. This is a cheap and simple method to freeze the stem cells for a short period in resource-constrained setting.