Long-term engraftment stability of peripheral blood stem cells cryopreserved using the dump-freezing method in a-80 degrees C mechanical freezer with10% dimethyl sulfoxide

In this study, we summarize our long-term follow-up data of 24 patients who underwent autologous peripheral blood stem cell transplantation (PBSCT) us ing the dump-freezing method in a -80 degreesC freezer. Collected periphera l blood mononuclear cells were mixed with a cryoprotectant solution consist ing of autologous plasma and 20% dimethyl sulfoxide, then placed in a -80 d egreesC freezer. The recovery rate of mononuclear cells (MNCs), colony-form ing unit-granulocyte/macrophage (CFU-GM) colonies, and CD34(+) cells were c alculated. Engraftment time (with neutrophil count > 0.5 x 10(9)/L, platele t count > 50 x 10(9)/L) and normal hemopoiesis (neutrophil count > 2 x 10(9 )/L, platelet count > 100 x 10(9)/L) were evaluated. Median duration of cry opreservation 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, respect ively. The median normal hemopoiesis times of neutrophil and platelet were 31 and 45 days, respectively. Nine patients are alive and in complete remis sion (CR). Seven patients in first CR sustained normal hemopoiesis with a m edian duration of 35 months. Two patients, who achieved second CR after sal vage chemotherapy due to a leukemia relapse after PBSCT. maintained engraft ment status for 24 and 28 months, and 1 reached normal hemopoiesis. These r esults demonstrate that PBSCT using the dump-freezing method in a -80 degre esC freezer leads to acceptable long-term engraftment stability. (C) 2001 T he Japanese Society of Hematology.