No clear benefit of cellular therapy consolidation for patients achieving remission after post-HCT AML relapse

Acute myeloid leukemia (AML) relapse after allogeneic hematopoietic stem cell transplant (HSCT) portends a dismal prognosis. One approach for reinvigorating a graft-versus-leukemia response is consolidation with donor lymphocyte infusions (DLI) or second HSCT (HSCT2). However, the role of DLI/HSCT2 in patients who achieve complete remission (CR) after salvage therapy is unclear. In this retrospective study, we evaluated the outcomes of 464 patients with post-HSCT AML relapse, focusing on those who achieved CR before consolidation with cellular therapy. In multivariable analysis (MVA), achieving CR after post-HSCT1 relapse was associated with improved overall survival (OS; hazard ratio [HR], 0.42; P< .0001). Of 133 patients (29%) who achieved CR after posttransplant AML relapse and before cellular therapy, 64 received DLI, 28 underwent HSCT2, and 41 received neither. Four-year outcomes from CR for the entire cohort (n = 133) were: OS 29%, relapse-free survival (RFS) 22%, cumulative incidence of relapse 58%, and nonrelapse mortality (NRM) 20%. In MVA, there was no association between receipt of DLI (HR, 0.87; P = .59) or HSCT2 (HR, 1.08; P = .83) and OS. Furthermore, we did not identify a benefit with DLI or HSCT2 with respect to RFS, relapse, or NRM. Patients with donor chimerism <90% at the time of CR had reduced 4-year OS (20% vs 32%; P = .03), as did measurable residual disease-positive patients (17% vs 62%; P = .024). Our results question the benefit of consolidation with DLI or HSCT2 in patients with AML who achieve CR, and we identify high-risk subgroups that should be the focus of future studies with larger cohorts.