[Clinical analysis of hypomethylating agent in preventing relapse after allogeneic hematopoietic stem cell transplantation in high-risk acute myeloid leukemia].

Objective: To explore the efficacy and feasibility of hypomethylating agent (HMA) as preventive therapy in children with high-risk acute myeloid leukemia (AML) after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Methods: A retrospective cohort study. Data from 173 children who underwent allo-HSCT for high-risk AML at Children's Hospital of Soochow University between August 2019 and April 2023 were analyzed. Participants were categorized into a trial group receiving HMA and a control group. Further classification was based on HMA courses:≥4 and <4 courses. The efficacy and safety of HMA preventive treatment after allo-HSCT were evaluated. Survival analysis was performed using the Kaplan-Meier method with Log-Rank testing, the Fine-Gray model was used to assess cumulative relapse rates and Cox regression was used to identify prognostic factors. Adverse events during HMA were descriptively analyzed. Results: Among 173 patients, there were 100 males (57.8%) and 73 females (42.2%), with the age of 81 (34,127) months. The starting time of HMA was 123 (91, 191) d post-transplant, continuing 4.0 (3.0, 6.5) courses and the follow-up period was 24 (13, 32) months. The trial group (53 cases) showed better 2-year overall survival (OS) rate ((88.6±5.6)% vs. (76.6±4.3)%, χ2=5.00, P=0.025) and relapse-free survival (RFS) rate ((89.2±4.7)% vs. (56.2±4.8)%, χ2=15.75, P<0.001) than control group (120 cases). The 2-year OS rates and RFS rates were similar between ≥4 courses group (31 cases) and <4 courses group (22 cases)(both P>0.05). The cumulative relapse rate in the trial group was significantly lower ((10.8±0.2)% vs. (35.2±0.2)%, χ2=10.84, P=0.001) than control group. Among children with molecular relapse, 8 cases (8/30, 26.7%) in the control group had hematological relapse compared to 1 case (1/2) in the trial group (χ2=0.81,P=0.369). The differences in incidence of acute and chronic graft-versus-host disease (GVHD) were not statistically significant (all P>0.05). Cox regression analysis revealed that minimal residual disease (MRD) positivity detected by flow cytometry before allo-HSCT and chronic GVHD were independent risk factors for OS (both P<0.05).The HMA preventive treatment was an independent protective factor for RFS, while age ≥10 years and MRD positivity detected by PCR before allo-HSCT were independent risk factors for RFS (all P<0.05). In trial group, 38 cases experienced grade 3 to 4 adverse events (71.7%). Conclusion: HMA is safe as preventive treatment in post-transplant children with high-risk AML, which can reduce the relapse risk and doesn't increase the risk of GVHD.