Non-cryopreserved hematopoietic stem cell transplantation compared to conventional autologous peripheral stem cell transplantation with cryopreserved stem cells among patients newly diagnosed with myeloma.

Hematopoietic stem cells are traditionally cryopreserved (CP) until transfusion. Melphalan's half-life is 75 min and allows transplantation of fresh non-CP hematopoietic stem cells (HSCs). There are a few studies in lymphoma and myeloma focusing on the role of autologous stem cell transplantation (ASCT) with fresh HSCs. In this single-center study, we aimed to compare the engraftment kinetics of non-CP versus conventional ASCT. Of 125 transplants performed among 121 myeloma patients, 44 were with conventional CP, while 81 were using non-CP products. Four patients with high-risk myeloma received tandem ASCT with non-CP followed by CP products. Non-CP patients compared to CP received similar induction regimens but more frequent Plerixafor (50.6% vs. 19%, p < 0.001) resulting in higher CD34 cell mobilization and transfusion (8.32 vs. 5.2 ×10⁶/kg, p < 0.001). Neutrophil and platelet engraftments between CP vs. non-CP groups were 11 (9-17) vs. 11.5 (10-19) days (p < 0.001) and 11 days (p = 0.31) in both, respectively. Complications such as mucositis and diarrhea of all grades were similar, but infusion-related reactions (15.9% vs 2.5%, p = 0.009) were more frequent with longer hospital stays (15 vs 14 days, p = 0.019) among CP compared to non-CP ASCTs. In conclusion, a statistically significant but clinically not meaningful faster neutrophil engraftment, fewer infusion-related reactions, and one day shorter duration of hospitalization were observed, all in favor of non-CP products, which also happens to coincide with more frequent use of plerixafor in our experience.