Abstract
Background: Programmed cooling - 196℃ liquid nitrogen preservation and non- programmed cooling - 80℃ low temperature refrigerator preservation have been widely used in Auto- HSCT. Programmed cooling and - 196℃ liquid nitrogen preservation can set the rate of temperature fall in advance and standardize the cooling process, reducing the damage to hematopoietic stem cells caused by temperature fall. But programmed cooling is a time-consuming process and it needs to purchase expensive control rate freezer. Non- programmed cooling - 80℃ low temperature refrigerator preservation is easy to operate, but it cannot keep a long preservation period. Since 2002, we tried combining two preservation methods into one: first we placed freezer bags in - 80℃ low temperature refrigerator and then placed them in -196℃ liquid nitrogen tank for long-term preservation, with the purpose of prolonging the cryopreservation of stem cells.
Method:We observed the influence of cryopreservation of hematopoietic stem cells with ladder-style freezing from low temperature refrigerator to liquid nitrogen in transplantation treatment of hematological malignancies, and analyzed the survival condition of patients after hematopoietic stem cell transplantation.We retrospectively analyzed the clinical datas of 98 patients with hematological malignancies treated by hematopoietic stem cell transplantation from 2002-01 to 2016-12 in our center.
Results: 98 patients, 56 males and 42 females, aged 14-69 years (avenge age36.46±14.19 years). Disease subtypes: 10 cases of acute lymphoblastic leukemia(ALL), 24 cases of acute non- lymphoblastic leukemia(ANLL) , 11 cases of multiple myeloma(MM), 53 cases of malignant lymphoma(ML). One case failed in implantation due to intracranial hemorrhage and the other 97 cases all succeeded in hematopoietic reconstitution. The median survival time was 47 months and the average follow-up time was 50.11 months. The average time needed to neutrophil count ≥0.5×109/L was 9.24±1.89d, and the average time needed to platelet count≥20×109/L without platelet transfusion for 3 days was 11.04±1.84d. The median survival time was 47.6 months (1~80 months). The overall survival rates of 1 year, 3-year and 5-year were (97.2±1.9) %, (84.2±4.6) % and (77.8±5.6) %, respectively. PFS (progression-free survival) of patients in 3 years and 5 years were (74.4±5.1)% and (61.2±6.2)% (Figure1), which is consistent with data reported by other transplantation centers. In this study, it is found that the application of auto-HSCT has significantly improved OS and PFS of patients with acute leukemia, malignant lymphoma and multiple myeloma, but there is no significant difference in OS and PFS among three groups(Figure2)(P=0.537). The survival condition of CR1 patients was better than no-CR1 patients(Figure3). The complication about transplantation mainly were digestive tract symptoms. 9.18% patients complicated with liver function injury and 58.16% patients got infection.We continuously improved cryophylactic agent and obtained cryoprotectant formed by 3%hydroxyethyl starch, 4% albumin and 5% DMSO to replace the traditional 10% DMSO cryoprotectant used in programmed cooling. During stem cell infusion, the occurrence rate of complication was 8.16%, significant lower than the occurrence rate of adverse events occurring in the usage of 10% DMSO cryoprotectant.
Conclusions: ladder-style freezing from low temperature refrigerator to liquid nitrogen with cryoprotectant that is formed by 3% hydroxyethyl starch, 4% albumin and 5% dimethyl sulfoxide (DMSO) for cryopreservation of hematopoietic stem cells. It can reach the same clinical transplantation effect with traditional programmed cooling freezing method in autologous hematopoietic stem cells transplantation (auto-HSCT) and can effectively improve OS, PFS of hematological malignancies.
No relevant conflicts of interest to declare.
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