Post Hematopoietic Cell Transplantation Maintenance Therapy With Low-Dose Azacitidine in a Pediatric Population With High-Risk Myeloid Malignancies.

[BACKGROUND] Patients with acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS) with high-risk features undergoing hematopoietic cell transplantation (HCT) experience high rates of relapse. Hypomethylating agent azacitidine (AZA) has been explored as post-HCT maintenance therapy at low doses to prevent relapse based on its potential for clinical efficacy and enhancing the graft-versus-leukemia effect.

[OBJECTIVE] To better understand the feasibility, tolerability, and efficacy of post-HCT maintenance AZA in a pediatric population with high-risk myeloid malignancies who underwent allogeneic HCT.

[STUDY DESIGN] A retrospective analysis was conducted of 24 pediatric patients (median age 12.4 years) with high-risk myeloid malignancies who received post-HCT AZA at a single institution. Descriptive measures were used to summarize participant characteristics. Point estimates of overall survival (OS) and relapse-free survival (RFS) were obtained using the method of Kaplan and Meier. Point estimates of relapse and non-relapse mortality were summarized using cumulative incidence estimates.

[RESULTS] AZA began at a median of 81 days post-HCT. The AZA dose ranged between 32-50 mg/m x 5 days and AZA continued for a median of 9 cycles. No significant myelosuppression or hospitalizations attributed to AZA were observed. Eighteen patients (75%) were diagnosed with grade II acute graft-versus-host disease (GVHD) before AZA initiation; 3 (16.7%) experienced ≤ grade II acute GVHD flares while tapering immunosuppressive treatment (IST) and receiving AZA. Of the 20 patients in remission at 1-year post-HCT, 18 (90%) had completed or were tapering IST. Six patients relapsed and the 3-year point estimate of relapse was 27%. There were 3 deaths due to relapsed disease. The 3-year point estimate of OS was 91% (one of the 3 deaths occurred beyond 3 years, at 3.2 years) and the 3-year estimate of RFS was 73%. The median follow-up among the 21 surviving patients was 29 months (range 12 to 80).

[CONCLUSIONS] This is the largest reported pediatric cohort receiving post-HCT prophylaxis with AZA. Our findings suggest AZA is tolerable with limited toxicity post-HCT and can be administered to pediatric patients with myeloid malignancies as maintenance therapy. Outcomes were favorable warranting further study.