Factors Associated with Efficient Harvesting and Engraftment of Auto-Transplants in Multiple Myeloma Patients

Background. The success of autologous hematopoietic stem cell transplantation (auto-HSCT) depends on the speed of transplant engraftment which in turn is affected by the count of harvested and infused hematopoietic stem cells (HSC). Aim. To identify predictors of auto-HSCT efficacy in multiple myeloma (MM) patients under introduction of new drugs at the phase of HSC induction and mobilization. Materials & Methods. The results of auto-transplant harvesting and engraftment were retrospectively analyzed in 75 MM patients during 112 auto-HSCTs. Auto-transplants were harvested using cyclophosphamide and vinorelbine combined with granulocyte colony-stimulating factor (G-CSF) without plerixafor. Conditioning regimen included melphalan 200 mg/m² or 140 mg/m², and combination of tiothepa with melphalan. All patients received subcutaneous injections of G-CSF in post-transplantation period. Transplant engraftment was assessed according to absolute neutrophil count of ≥ 0.5 ^x 10⁹/L, and thrombocyte count of ≥ 20 x 10⁹/L. Results. It is established that the predictors of a high CD34⁺ cell count in auto-transplant are a single previous induction regimen (p = 0.0315) and administration of cyclophosphamide in mobilization regimen (p = 0.0001). Transplant engraftment period is determined by auto-HSCT serial number and amount of infused CD34⁺ cells. Hematopoiesis regeneration after the second auto-HSCT was accelerated by more frequent use of Mel140 (p = 0.001). Conclusion. Auto-transplant quality and engraftment period in MM patients primarily depend on the efficacy of induction therapy and the intensity of HSC mobilization regimen. Therefore, induction therapy and mobilization regimen need to be tailored to an individual patient, MM prognostic variant, probability of response to standard induction regimens, and the number of planned auto-HSCTs.