Survival following relapse after allogeneic hematopoietic cell transplantation for acute leukemia and myelodysplastic syndromes in the contemporary era.

Objective/background: Relapse is the most common cause of treatment failure after allogeneic hematopoietic cell transplantation (alloHCT). No standard of care exists, and a wide range of treatments are used for post-alloHCT relapse. In the recent era, several novel therapies including targeted agents are available for acute lymphocytic leukemia (ALL), acute myeloid leukemia (AML), and myelodysplastic syndrome (MDS).

Methods: We reviewed outcomes after alloHCT relapse, with or without use of these newer agents for ALL, AML, and MDS. In total, 115 adults with relapsed or refractory ALL (n = 17), AML (n = 67), and MDS (n = 31) at median 5 (range, 1-64) months after their first alloHCT in 2010-2018 were included.

Results: Median follow-up was 19 (range, 6-80) months after relapse from alloHCT. Targeted agents were given to 29 (25%) patients. In multivariable analysis, use of targeted agent at any time point after relapse was not associated with survival. Matched unrelated (vs. matched sibling; hazard ratio [HR] 1.70; p = .027) or haploidentical donor grafts (vs. matched sibling; HR 2.69; p = .003), presence of grade II-IV acute graft-versus-host disease before relapse (HR 2.46; p < .001), and less than 12 months from HCT to relapse (<6 vs. > 12 months; HR 6.34; p < .001; 6-12 vs. > 12 months; HR 3.16; p = .005) were adverse prognostic factors for post-relapse survival.

Conclusion: Outcomes after alloHCT relapse remain poor regardless of the novel agent use. Innovative treatment strategies are needed to improve outcomes after relapse post-alloHCT.