Post-transplant cyclophosphamide (PTCy)-based prophylaxis for graft-versus-host disease (GVHD) is widely used in HLA-haploidentical hematopoietic cell transplantation (haplo-HCT). One of the major drawbacks of PTCy is the risk of rare but potentially lethal cardiotoxicity, which prompted the development of regimens with reduced doses of PTCy.
We retrospectively compared the incidence of early cardiotoxicity with standard-dose of PTCy (cyclophosphamide 50 mg/kg/day for 2 days, PTCy100) versus reduced-dose (40 mg/kg/day for 2 days, PTCy80). In total, 179 patients underwent PTCy-based haplo-HCT, including PTCy100 (n = 111) and PTCy80 (n = 68).
The PTCy80 group included significantly more elderly patients, patients who received reduced-intensity conditioning, and patients with a history of HCT than the PTCy100 group. Nine eligible patients (5.0%) experienced severe cardiotoxicity. The incidence of severe cardiotoxicity did not differ significant between PTCy80 and PTCy100 (4.4% vs. 5.4%; p = 1). The incidence of fatal cardiotoxicity was lower with PTCy80, but the small size may have prevented the difference from reaching statistical significance.
Reducing the cyclophosphamide dose in PTCy-based GVHD prophylaxis may lower the risk of fatal cardiotoxicity without significantly altering the overall incidence of severe cardiotoxicity.

© 2025. The Author(s), under exclusive licence to Japanese Society of Hematology.