Azacitidine and prophylactic donor lymphocyte infusions after hematopoietic stem cell transplantation for pediatric high-risk acute myeloid leukemia

[Preventive and therapeutic strategies for relapse after hematopoietic stem cell transplant for pediatric AML (SFGM-TC)]

Treatment of pediatric high-risk acute myeloid leukemia (AML), defined either on molecular or cytogenetic features, relies on bone marrow transplant after cytologic remission. However, relapse remains the first post-transplant cause of mortality. In this 13th session of practice harmonization of the francophone society of bone marrow transplantation and cellular therapy (SFGM-TC), our group worked on recommendations regarding the management of post-transplant relapse in AML pediatric patients based on international literature, national survey and expert opinion. Overall, immunomodulation strategy relying on both measurable residual disease (MRD) and chimerism evaluation should be used for high-risk AML. In very high-risk (VHR) AML with a 5-year overall survival ≤30 %, a post-transplant maintenance should be proposed using either hypomethylating agents, combined with DLI whenever possible, or FLT3 tyrosine kinase inhibitors if this target is present on leukemia cells. In the pre-emptive or early relapse settings (< 6 months post-transplant), treatments combining DLI, Azacytidine and Venetoclax should be considered. Access to phase I/II trails for targeted therapies (menin, IDH or JAK inhibitors) should be discussed in each patient according to the underlying molecular abnormalities of the disease.

Navigating Treatment Options and Communication in Relapsed Pediatric AML

Despite improved outcomes in newly diagnosed pediatric AML, relapsed disease remains a therapeutic challenge. Factors contributing to slow progress in improving outcomes include inherent challenges in pediatric clinical trial accrual and the scarcity of novel targeted/immunotherapy agents available for pediatric development. This paradigm is changing, however, as international collaboration grows in parallel with the development of promising targeted agents. In this review, we discuss the therapeutic landscape of relapsed pediatric AML, including conventional chemotherapy, targeted therapies, and the challenges of drug approvals in this patient population. We highlight current efforts to improve communication among academia, industry, and regulatory authorities and discuss the importance of international collaboration to improve access to new therapies. Among the therapeutic options, we highlight the approach to second hematopoietic stem cell transplant (HSCT) and discuss which patients are most likely to benefit from this potentially curative intervention. Importantly, we acknowledge the challenges in providing these high-risk interventions to our patients and their families and the importance of shared communication and decision making when considering early-phase clinical trials and second HSCT.

Treatment of recurrent pediatric myelodysplastic syndrome post hematopoietic stem cell transplantation

Treatment of recurrent myelodysplastic syndrome (MDS) after hematopoietic cell transplantation (HCT) remains challenging. We present a 4-year-old girl experiencing early MDS relapse post-HCT treated with a multimodal strategy encompassing a second HCT and innovative targeted therapies. We underscore the potential of a comprehensive treatment approach in managing recurrent pediatric MDS.

Efficacy of Azacitidine and Prophylactic Donor Lymphocyte Infusion after HSCT in Pediatric Patients with Acute Myelogenous Leukemia: A Retrospective Pre-Post Study

Pediatric patients with acute myeloid leukemia (AML) who undergo allogeneic hematopoietic stem cell transplantation (HSCT) continue to have high rates of relapse. In 2018, Phoenix Children's Hospital started using post-HSCT maintenance therapy in patients with AML in attempt to decrease the number of relapses after HSCT. This therapy consisted of the hypomethylating agent azacitidine (AZA; 6 cycles starting on day +60) and prophylactic donor lymphocyte infusion (DLI; 3 escalating doses beginning after day +120). We aimed to compare 2-year leukemia-free survival (LFS) post-HSCT between patients with AML who received post-HSCT maintenance therapy with AZA and prophylactic DLI and historical control patients who did not receive post-HSCT therapy. This retrospective pre-post study was conducted at Phoenix Children's Hospital and included patients with AML who underwent HSCT between January 1, 2008, and May 31, 2022. We compared LFS, overall survival (OS), and immune reconstitution patterns post-HSCT between patients with AML who received post-HSCT maintenance therapy with AZA and prophylactic DLI (postintervention group) and historical control patients who did not receive this post-HSCT maintenance therapy (preintervention group). Sixty-three patients were evaluable. After excluding 7 patients who died or relapsed prior to day +60, 56 patients remained, including 39 in the preintervention group and 17 in the postintervention group. The median age at transplantation was 9.1 years in the preintervention group and 11 years in the postintervention group (P = .33). The 2-year LFS was 61.5% in the preintervention group, compared to 88.2% in the postintervention group (P = .06). The 2-year OS was 69.2% in the preintervention group and 88.2% in the postintervention group (P = .15). The rates of CD3⁺CD4⁺ T cell and CD19⁺ B cell recovery were faster in the preintervention group compared to the postintervention group (P = .004 and .0006, respectively). In this limited retrospective study, post-HSCT maintenance therapy using AZA and prophylactic DLI was well tolerated; however, its efficacy is yet to be fully determined.

Antithymocyte Globulin Plus Post-Transplant Cyclophosphamide Combination as an Effective Strategy for Graft-versus-Host Disease Prevention in Haploidentical Peripheral Blood Stem Cell Transplantation for Children with High-Risk Malignancies

Haploidentical hematopoietic stem cell transplantation using post-transplant cyclophosphamide (PTCy) for graft-versus-host disease (GVHD) prophylaxis has emerged as a valid alternative transplant strategy for patients lacking a suitable HLA-matched related donor. The high risk of severe GVHD remains the major clinical challenge in this setting. The addition of antithymocyte globulin (ATG) in PTCy-based regimens for GVHD reduction in haploidentical hematopoietic stem cell transplantation is rational and was reported in adult series. However, its feasibility is unknown in pediatric patients. Here, we firstly describe our experience of 15 consecutive children with high-risk malignancies receiving haploidentical peripheral blood stem cell transplantation using ATG plus PTCy for GVHD prophylaxis. Only three patients developed grade 1-2 acute GVHD, limited to skin. No grade 3-4 acute GVHD and chronic GVHD were observed. Viral reactivations were frequently seen but manageable. Six patients relapsed, as the main cause of death in our series. None died from events related to GVHD. Our data suggest that ATG plus PTCy is an effective strategy for GVHD prevention in haploidentical peripheral blood stem cell transplantation and is feasible in children with high-risk malignancies.

Efficacy of azacitidine in preventing relapse after hematopoietic stem cell transplantation for advanced myeloid malignancies: a systematic review and meta-analysis

BACKGROUND

Relapse is the leading cause of death from myeloid malignancies after allogeneic hematopoietic stem cell transplantation (HSCT). Azacitidine has gained attention in recent years in the prophylaxis of relapsed refractory hematologic malignancies. This study evaluated the efficacy of AZA in preventing relapse after HSCT in patients with myeloid malignancies.

METHODS

A systematic review and meta-analysis of all available cohort studies were performed regarding the application of AZA for prophylaxis of relapse after HSCT for advanced MDS and AML. Databases were searched for relevant studies. Endpoints included 2-year relapse rate, survival, relapse-related mortality, as well as the incidence of graft-versus-host disease (GVHD).

RESULTS

A total of 444 patients from 13 studies were included in this analysis. The pooled estimate of the cumulative incidence of relapse after two years in enrolled patients was 25% (95% confidence interval [CI], 18%-33%). The pooled estimates of 2-year survival probabilities were 65% (95% CI, 50%-79%). The pooled cumulative incidence of relapse-related mortality was 28% (95% CI, 22%-34%). The pooled estimated incidence of acute and chronic GVHD, respectively, were 28% (95% CI, 22%-34%) and 38% (95% CI, 27%-49%).

CONCLUSION

AZA administration is efficacious for relapse prevention after HSCT in myeloid malignancies.