Retrospective, single-center analysis of second allogeneic stem cell transplantation versus non-transplant regimens for acute myeloid leukemia patients with relapse after first transplantation

Relapse of acute myeloid leukemia (AML) after first allogeneic stem cell transplantation (ASCT) is associated with a poor prognosis. While previous studies have focused solely on outcomes after a second ASCT (ASCT2) in this patient population, we aimed to compare the therapeutic efficacy of ASCT2 with transplant-free regimens. We retrospectively compiled a cohort of 143 AML patients who relapsed after ASCT1 and received either a second ASCT (n = 54) or a transplant-free regimen (n = 89, no-ASCT2). All patients were transplanted at our institution between 2007 and 2023. After a median follow-up of 5.8 months starting from time of relapse, ASCT2 patients experienced significantly better overall survival (OS) in a univariate Kaplan-Meier analysis (p = 0.002). Median OS was 425 days for ASCT2 as opposed to 80 days for the no-ASCT2 group. One- / two-year survival rates were 53.1% / 39.0% and 30.0% / 22.3% for ASCT2 and no-ASCT2 patients, respectively. In a multivariate model accounting for immortal time bias, ASCT2 was still associated with improved survival (time ratio 2.13, p = 0.164), although this result did not reach statistical significance. Among patients who underwent ASCT2, complete remission prior to transplantation was the strongest independent predictor of survival. Lastly, non relapse mortality rates were significantly higher for ASCT2, whereas mortality was dominated by relapse deaths for no-ASCT2 patients. We conclude that ASCT2 could potentially be superior to no-ASCT2 treatment strategies, especially in fit patients who achieve a CR prior to ASCT2. Larger, prospective studies are warranted to validate these findings.