CD34+ hematopoietic progenitor cell dose as a predictor of engraftment and survival in multiple myeloma patients undergoing autologous stem cell transplantation

Background/aim: High-dose melphalan and autologous hematopoietic stem cell transplantation (AHSCT) is the standard treatment strategy for multiple myeloma (MM) patients who are eligible for it. The recommended dose of CD34+ hematopoietic progenitor cells (HPCs) for adequate engraftment is above 2 × 106/kg. The aim of this study was to evaluate the relationship between the dose of CD34+HPCs and survival in MM patients who underwent AHSCT at a tertiary care center. Materials and methods: Enrolled in this study were 271 MM patients who underwent AHSCT between 2003 and 2019. Clinical characteristics of the patients, disease status pre-AHSCT, reinfused CD34+ cell doses, and neutrophil and platelet engraftment days were recorded, retrospectively. The patients were divided into 2 groups according to whether the dose of reinfused CD 34+ HPCs was <5 × 106/kg or ≥5 × 106/kg. The groups were compared in terms of engraftment and overall survival (OS) times. Results: The median age of the patients was 54.8 (33­76) years. The median dose of infused CD34+ HPCs was 5.94 × 106/kg (1.47­59.5 × 106/kg). The median follow-up period was 54 months (4­211). The median OS of the patients was 103 months (11­144). The median neutrophil and platelet engraftment time was 10 (8­24) and 11 (7­40) days. Doses of <5 × 106/kg and ≥5 × 106/kg CD34+ HPC were reinfused in 38.1% and 61.9% of the patients, respectively. There was a negative significant correlation between the reinfused CD34+cell level and neutrophil/platelet engraftment times (r = ­0.32, P < 0.001; r = ­0.27, P < 0.001, respectively). The median OS times were observed as 103 months (11­144) and 145 months (123­166) for patients who had been administered <5 × 106/kg and ≥5 × 106/kg of CD34+ HPCs, respectively (P = 0.009). Conclusion: The increased amount of CD34+ autologous hematopoietic stem cell dose after high dose melphalan chemotherapy in MM patients shortened the platelet and neutrophil engraftment time and increased OS. Early platelet engraftment and administration of a CD34+ HPC count that is ≥5 × 106/kg can be considered as predictors of better survival in patients.