Anurag Kumar Singh

In allogeneic hematopoietic cell transplantation with post-transplant cyclophosphamide (PTCy), clinicians frequently face a critical choice between a readily available, often younger, haploidentical and a fully matched unrelated donor (MUD). The platform-specific influence of donor age on survival is a critical, unquantified factor that complicates clinical decision-making. We retrospectively analyzed 4258 adult patients with acute leukemia who underwent first allogeneic HCT with PTCy (2017-2021). We employed machine learning (Random Survival Forests and DeepSurv) alongside robust regression models, including Inverse Probability of Treatment Weighting, 1:1 Propensity Score Matching, and Elastic-Net penalized Cox regression. Machine learning models revealed a divergent association of donor age with survival depending on donor type. The MUD-PTCy platform proved remarkably resilient; a 1% absolute increase in mortality risk (equivalent to Number-Needed-to-Harm of 100) did not emerge in donors up to age 50. In stark contrast, the age-sensitive Haploidentical cohort reached this same risk threshold at a donor age of just 38 years. MUD-PTCy was independently associated with a significant overall survival advantage (Adjusted Hazard Ratio 0.85; 95% confidence interval, 0.75–0.97; P = 0.01). This analysis provides a quantitative framework to guide the trade-off between HLA matching and donor age, supporting individualized decision-making and a rationale to reconsider restrictive donor age policies.

Allogeneic hematopoietic cell transplantation (HCT) is the only curative therapy for myelofibrosis (MF) and is recommended for patients with higher risk disease. However, there is a risk of early mortality, and optimal timing is unknown. JAK inhibitor (JAKi) therapy may offer durable improvement in symptoms, splenomegaly and quality of life. The aim of this multicentre, retrospective observational study was to compare outcomes of patients aged 70 years or below with MF in chronic phase who received upfront JAKi therapy vs. upfront HCT in dynamic international prognostic scoring system (DIPSS)-stratified categories. For the whole study cohort, median overall survival (OS) was longer for patients who received a JAKi vs. upfront HCT, 69 (95% CI 57–89) vs. 42 (95% CI 20–not reached, NR) months, respectively (p = 0.01). In patients with intermediate-2 and high-risk disease, median OS was 55 (95% CI 36–73) months with JAKi vs. 36 (95% CI 20–NR) months for HCT (p = 0.27). An upfront HCT strategy was associated with early mortality and difference in median OS was not observed in any risk group by 5 years of follow-up. Within the limitations of a retrospective observational study, we did not observe any benefit of a universal upfront HCT approach for higher-risk MF.

Disclosures. Mahmoudjafari:Omeros: Speakers Bureau; Pfizer, Genentech, Inc., BMS, KITE, Sanofi, Janssen: Honoraria; Genentech, Inc.: Consultancy. Ahmed:Kite/Gil

Background: Patients who do not have a human leukocyte antigen (HLA)-matched donor can undergo hematopoietic stem cell transplantation (HSCT) by utilizing haploidentical (haplo) family donors and post-transplant cyclophosphamide (PTCy) for Graft-versus-host disease (GVHD) prophylaxis. Originally, Haplo transplants utilized a bone marrow (BM) source because of concern of higher incidence of GVHD with peripheral blood stem cells (PBSC) graft. Recent years have seen an increase in PBSC graft utilization. Some published studies have reported comparable survival between the two graft sources. These studies also reported lower rate of chronic GVHD and higher quality of life with BM and a lower relapse rate and faster engraftment with PBSCs. We aimed to investigate the outcomes following BM versus PBSC haplo HSCT using (PT-Cy)-based GVHD prophylaxis. Methods: In this single-center retrospective study, we included all (n=176) adult patients who underwent haplo HSCT from August 2016 to July 2021 and had at least one year of follow-up. Bivariate analyses, using the chi-square and t-test, were performed. Kaplan-Meier and regression analyses were conducted. Data were analyzed using SPSS version 28. Statistical significance was considered at p<0.05. Results: The study included 176 haplo transplants including 65% peripheral blood and 35% bone marrow grafts. The median age was 54 (18-74) years and 68% of recipients were males. Ethnic minorities comprised 30% of recipients. Hematologic diagnoses included myeloid disease (65%), lymphoid disease (29%), and others (6%). 31 % of the patients underwent a Myeloablative transplant. Hematopoietic cell transplantation comorbidity index of 3 or higher was noted in 53% of patients. With a Median follow-up 21 (0-73) months, Overall survival (OS) and disease-free survival (DFS) was not reached in either BM or PBSC haplo HSCT group. 1-year OS of 75% and 74% (p-0.898) and 1-year DFS of 63% and 63% (p-0.994) were noted in BM and PBSC group respectively. In PBSC versus BM haplo recipients, an earlier neutrophil engraftment (17 days vs 18 days, p=0.022) was seen. Similar incidences of grade II-IV acute GVHD (50% vs 51%, p=0.875), relapse (22% vs 26%, p=0.579), non-relapse mortality (NRM, 17% vs 20%, p=0.682), platelet engraftment (28 vs 31 days, p<0.092) and 1- year chronic GVHD (35% vs 38%, p=0.410) were noted. Conclusions: In this study, Haploidentical allogeneic hematopoietic stem cell transplant recipients demonstrated similar rates of overall and disease-free survival, relapse, non-relapse mortality, acute and chronic GVHD, and platelet engraftment regardless of graft source. Neutrophil engraftment was observed one day earlier in peripheral stem cell recipients. This supports the use of either PBSC or Bone marrow as the preferred source of Haploidentical transplants.