Prophylactic donor lymphocyte infusions (DLI) are part of the sequential FLAMSA-reduced intensity conditioning (RIC) regimen to cure acute myeloid leukemia with allogeneic hematopoietic stem cell transplantation (HSCT). Although DLI themselves carry significant risks, their prophylactic use has not been analyzed in a time-dependent manner.

114 patients underwent FLAMSA-RIC HSCT between 2013-2020. Next to Kaplan Meier estimation of overall, disease free and graft-versus-host-relapse-free survival (OS, DFS, GRFS), cumulative incidences of relapse and death in remission were calculated in a competing risk model. Additionally, the contribution of prophylactic and preemptive DLI as time-dependent covariates was assessed using a time-varying model towards DFS (Simon-Makuch method, Mantel-Byar test).

At two years, OS was 45.2% [95%CI 36.7–55.7%], DFS 31.8% [95%CI 24–42.2%] and GRFS 11.3 [95%CI 6.5–19.8]. Neither prophylactic nor preemptive DLI showed a significant influence on DFS when considered time-dependent covariates (Mantel-Byar, p=0.3). This was further corroborated in competing risk analysis with DLI as time-dependent covariates.

Both prophylactic and preemptive DLI fail to significantly impact survival within a high-risk-cohort in a time-varying model. Controlled trials to address the impact of post-grafting immunotherapy approaches are needed.