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 (33–76) years. The median dose of infused CD34+ HPCs was 5.94 × 106/kg (1.47–59.5 × 106/kg). The median follow-up period was 54 months (4–211). The median OS of the patients was 103 months (11–144). The median neutrophil and platelet engraftment time was 10 (8–24) and 11 (7–40) 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 (11–144) and 145 months (123–166) 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.