UTILIZATION OF STORED PERIPHERAL BLOOD STEM CELLS TO SUPPORT SECOND HEMATOPOIETIC STEM CELL TRANSPLANTATION

Abstract

Aim: Hematopoietic Stem Cell Transplantation (HSCT) is used to treat or cure a wide spectrum of conditions. Cryopreservation maintains the therapeutic properties of Peripheral Blood Stem Cells (PBSC), allowing clinical, regulatory, and logistical procedures needed for successful HSCT. Complications of mobilizing and collecting additional PBSC following recovery from the myeloablative HSCT have led centers to adopt the practice of collection and storage of enough PBSC for two HSCTs. However, the collection, cryopreservation, and storage of extra PBSC than that needed for a single HSCT have logistical, infrastructure, and cost issues. Here, we evaluated the collection, storage, and utilization practices of PBSC for two or more HSCTs. Methods: This cross-sectional study included patients referred for HSCT at eight transplant centers. Cryopreservation, storage, and other laboratory procedures were conducted at Cetebio/Fundação Hemominas between 2013 and 2022. Frozen cells were stored in the vapor phase of nitrogen. The records were reviewed to obtain information the regarding the patients and frozen cell therapy products. Results: Cetebio released frozen PBSC for 1,311 transplantations between 2013 and 2022. Two hundred fifty patients had 321 bags with residual PBSC in storage after their first HSCT (234 autologous and 16 allogeneic HSCT). Patients had a mean age of 49.6 ± 3.4 years, and most were male (162; 64.8%). Most (200; 80%) had Multiple Myeloma (MM), followed by leukemia (18; 7.2%), Germ Cell Tumor (GCT, 14; 5.6%), and other diagnoses (18; 7.2%). Cells from 66 (26.4%), 163 (65.2%), and 21 (8.4%) patients were frozen 2 years or less ago, 2.1 to 7 years ago, and more than 7 years ago, respectively. Thirty-three bags from 24 (9.6%) patients were released for a second HSCT within a median of 2.2 years after the cryopreservation. The mean age of patients at the time of the second HSCT (23 autologous and one allogenic transplantation) was 51.6 ± 14.4 years, ranging from 18 to 69 years. Most were male (15; 62.5%) and had MM (15; 62.5%) followed by GCT (5; 20.8%), leukemia (3; 12,5%), and myelodysplastic syndrome (1; 4.2%). The remaining 288 frozen bags continue stored at our facility and represent about a third of our tank storage capacity. The human, infrastructure, and economic resources required to cryopreserve and store unused PBSC are equivalent to the resources needed to attend nearly 144 extra patients. Discussion: The frequency of second transplantation was similar to previously published studies (9% to 19%). This study is limited by its retrospective design and the relatively short-term follow-up. Some frozen PBSCs will probably be released for a second HSCT in the future. Nevertheless, in public healthcare systems, resources should be used based on equity and effectiveness. Since most patients probably never undergo a second HSCT, our institution changed its practices regarding PBSC collection, cryopreservation, and storage to support the second HSCT. Currently, it is allowed only for diseases that benefit from tandem infusions. Conclusions: this study showed a low utilization of stored PBSC to support the second HSCT. The results suggest a review of practices regarding cryopreservation PBSCs for a second HSCT, especially in public healthcare system settings and places where novel agents and new therapeutic approaches for treatment of MM are available.