Retrospective study of impact of graft-versus-host-disease prophylaxis on long-term outcomes in patients surviving beyond two years after alloHSCT

A retrospective study at the University of Toronto (Canada) evaluated the impact of graft-versus-host disease (GVHD) prophylaxis on long-term outcomes in patients surviving beyond 2 years after allogeneic transplantation (alloHSCT) for hematological cancers. The study included 874 relapse-free survivors at 2 years who underwent alloHSCT between 2010 and 2022. GVHD prophylaxis included post-transplant cyclophosphamide (PTCy) plus rabbit antithymocyte globulin (ATG) and a calcineurin inhibitor (CnI) in group I (=429) or alternative regimens (group II, n=445). With an overall follow-up of 5275 person-years after HSCT, overall survival rate 3 years after the landmark was 88.7% (95% CI 86-91), with better outcomes in group I compared to group II (93.2% versus 85.1%; p<0.001). Group I also had lower nonrelapse mortality (NRM) rate than group II (3.8% versus 10.8%; p<0.001). On multivariable analysis, ATG-PTCy-CnI was independently associated with improved OS (HR 0.41; p=0.007) and lower NRM (HR 0.34; p=0.006). Deaths from GVHD, infections, treatment-related toxicity, and second primary malignancies were all reduced with ATG-PTCy-CnI. The cumulative incidence of relapse was similar between groups. The authors conclude that among patients alive and relapse-free at least 2 years after alloHSCT, long-term outcomes were excellent; the use of ATG-PTCy-CnI prophylaxis was associated with further inprovement in survival.