Allogeneic hematopoietic cell transplantation for patients with a history of multiple relapses of acute myeloid leukemia

The prognosis of patients with acute myeloid leukemia (AML) is dismal after experiencing multiple relapses. This study retrospectively analyzed outcomes of allogeneic hematopoietic cell transplantation (HCT) for 192 adults with AML in third or subsequent complete remission (CR3+), 300 in second relapse (REL2), and 50 in third or subsequent relapse (REL3+) who were enrolled in a Japanese nationwide transplantation registry. The study population included patients undergoing umbilical cord blood transplantation, but not those undergoing haploidentical HCT. Patients transplanted in CR3+ had better survival than those transplanted in REL2 and REL3+ (48%, 21%, and 12% at 4 years; P < 0.001), and this was due to a reduction in post-transplant relapse (23%, 57%, and 52%; P < 0.001). The corresponding cumulative incidence of non-relapse mortality was 33%, 26%, and 36% (P = 0.022). Multivariate analysis revealed significantly lower relapse and overall mortality for those in CR3+ and significantly lower non-relapse mortality for those in REL2. Hazard ratios (95% confidence intervals) for overall mortality were 2.02 (1.56–2.64) for REL2+ versus CR3+ (P < 0.001) and 2.12 (1.40–3.19) for REL3+ versus CR3+ (P < 0.001). Our analysis demonstrates the curative potential of allogeneic HCT for patients with a history of multiple AML relapses and suggests the potential benefits and risks of reinduction attempt before transplantation, highlighting the need for an individualized approach in determining whether to give reinduction therapy in this setting.