Long-Term Hematologic Reconstitution and Clinical Evaluation of APBSCT with Cryopreservation of Stem Cells with 5- and 10-Percent DMSO at -80°C Mechanical Freezer.

Current protocols for cryopreservation prior to autologous peripheral blood stem cell transplantation (APBSCT) are usually based on 10% DMSO as an intracellular cryoprotectant with or without HES as extracellular cryoprotectant. The toxic effects related to DMSO infusion are usually dose-related and mild but can be severe including blood pressure alterations and arrhythmia. HES is a relatively nontoxic drug but it is related with pruritus and nephrotoxicity. Cryopreservation is usually performed by controlled-rate methods, followed by storage in liquid nitrogen. These procedures are time consuming and require expensive devices. Ten years ago we described a simplified cryopreservation technique at −80°C without rate-controlled freezing followed by storage in the same mechanical freezer and with 5% or 10% DMSO concentrations as the sole cryoprotectant (without HES). We report now a long-term evaluation of our experience along 12 years. Between July 1993 and September 2004, we performed 297 consecutive APBSCT for patients with solid and hematologic malignancies. Grafts were cryopreserved using 10% (n=47) and 5% (n=250) DMSO. Biological data of grafts, hematologic recovery and clinical data of cases were recorded. Special monitoring of infusion-related toxicity (IRT) was done. The median storage times were 31 and 28 days for 5% and 10% DMSO groups (p=NS). Post-thaw nucleated cell viability was 85% and 85.5% for 5% and 10% DMSO groups (p=NS). Patients included in the 5% DMSO group received a higher number of mononuclear and CD34+ cells. Criopreservation time did not significantly influence viability or hematopoietic recovery inside the criopreservation period (203 days or less). Significant IRT was higher in the 10% DMSO group: 21.3% versus only 7.2% in the 5% DMSO group (p=0.002), including hypertension, bradycardia, tachycardia, chest tightness and abdominal pain. Mild IRT was more than double in the 10% DMSO group: 10.6% versus 4% in the 5% DMSO group (p=0.07). No severe toxicities or death-related to infusion have been noted. All patients showed a safe and sustained engraftment. Median time to 500 and 1000 neutrophil/microL was the same in the two groups (11 days). Median time to 20 and 50 platelets/L was higher in the 5% vs 10% DMSO group: 12 vs 11 (p=0.03) and 17 vs 13 (p<0.001), respectively. Long-term hematologic recovery at 6, 12 and 24 months did not differ between the two groups studied and it was also comparable to standard rate-controlled freezing protocols. Factors influencing a faster neutrophil and platelet recovery in the multivariate analysis were infusion of more than 3 x 10⁶/Kg of CD34⁺ cells and a viability >60%. G-CSF administration from day +5 postransplant was also related with a faster neutrophil recovery. Transplantation-related mortality was 2.8% and 2.1% respectively for 5% and 10% DMSO groups (p=NS). Long-term clinical evaluation of autologous transplantation with blood stem cells cryopreserved with 5% or 10% DMSO at −80°C without rate-controlled freezing shows that these are feasible procedures with engraftment, hematologic reconstitution and outcomes comparable to standard rate-controlled freezing protocols. Significant and mild IRT were lower in the 5% DMSO group compared with the 10% DMSO group.