Long-Term Engraftment Stability of Peripheral Blood Stem Cells Cryopreserved Using the Dump-Freezing Method in a −80°C Mechanical Freezer with 10% Dimethyl Sulfoxide

Abstract

In this study, we summarize our long-term follow-up data of 24 patients who underwent autologous peripheral blood stem cell transplantation (PBSCT) using the dump-freezing method in a −80°C freezer. Collected peripheral blood mononuclear cells were mixed with a cryoprotectant solution consisting of autologous plasma and 20% dimethyl sulfoxide, then placed in a −80°C freezer. The recovery rate of mononuclear cells (MNCs), colony-forming unit—granulocyte/macrophage (CFU-GM) colonies, and CD34⁺ cells were calculated. Engraftment time (with neutrophil count > 0.5 × 10⁹/L, platelet count > 50 ×10⁹/L) and normal hemopoiesis (neutrophil count > 2 ×10⁹/L, platelet count > 100 ×10⁹/L) were evaluated. Median duration of cryopreservation was 76 days. The mean recovery rates of MNCs, CFU-GM colonies, and CD34⁺ cells were 93.4%, 78.4%, and 95.3%, respectively. The median engraftment times of neutrophils and platelets were 8 and 27 days, respectively. The median normal hemopoiesis times of neutrophil and platelet were 31 and 45 days, respectively. Nine patients are alive and in complete remission (CR). Seven patients in first CR sustained normal hemopoiesis with a median duration of 35 months. Two patients, who achieved second CR after salvage chemotherapy due to a leukemia relapse after PBSCT, maintained engraftment status for 24 and 28 months, and 1 reached normal hemopoiesis. These results demonstrate that PBSCT using the dump-freezing method in a −80°C freezer leads to acceptable long-term engraftment stability.