Eur J Haematol

Objective: This retrospective, single-center study aims to compare the efficacy and safety of a reduced dose of post-transplantation cyclophosphamide (PTCy) (60 mg/kg total dose) versus the standard dose (100 mg/kg total dose), both combined with tacrolimus, in adult patients undergoing allogeneic hematopoietic stem cell transplantation from HLA-matched related or unrelated donors.

Methods: We report clinical outcomes of 59 consecutive patients who received standard doses of PTCy and 48 with the new reduced dose.

Results: Neutrophil and platelet recovery occurred later in the standard-dose group (p < 0.01). The incidence of febrile neutropenia was higher in the standard-dose group (p < 0.01). No significant differences were found in the incidence of acute cardiac events, early bacteremia, CMV reactivation within the first 100 days post-HSCT, or the development of hemorrhagic cystitis. There were no significant differences in the incidence of grade II-IV and III-IV acute GvHD, moderate-to-severe chronic GvHD, or in 20-month overall survival and progression-free survival (p > 0.05). Non-relapse mortality at 100 days and at 1 year was comparable between groups, as was 1-year GVHD-free/relapse-free and immunosuppression-free survival (p > 0.05).

Conclusions: Reduced doses of CyPT combined with a single immunosuppressive agent are emerging as a safe and effective alternative for adult patients undergoing allo-HSCT from HLA-matched donors. Our findings support that this approach preserves key clinical outcomes while potentially reducing acute hematological and infectious toxicity.