Outcomes of Allogeneic Hematopoietic Cell Transplantation for Hypoplastic Myelodysplastic Syndrome: A Latin American...

The hypoplastic myelodysplastic syndromes (MDS-h), a rare subtype accounting for 10% to 15% of patients with myelodysplastic syndromes (MDS), is defined by a reduction of ≤25% bone marrow cellularity, age-adjusted according to the World Health Organization (WHO) 2022 classification. Allogeneic hematopoietic cell transplantation (HCT) should be considered in patients with MDS-h based on the severity of cytopenias, transfusion dependence, and failure of treatment. The objective of this study is to evaluate the clinical characteristics and transplantation outcomes of Latin American patients with MDS-h who underwent HCT and to compare these outcomes with those of patients with normocellular MDS (MDS-n) or hypercellular MDS (MDS-hyper).

This retrospective study included 458 patients who underwent HCT for MDS at diagnosis between 2012 and 2024, as reported by 38 centers from Brazil, Argentina, and Uruguay to the Latin American Registry. Categorical variables were compared using Chi-square or Fisher's tests. Survival was estimated using Kaplan-Meier analysis and compared using the log-rank test. Cox regression was used for multivariable analysis (R software v. 4.2.1; P < .05).

Among a total of 458 patients, 69 (15.07%) were diagnosed with MDS-h, whereas 389 (84.93%) had MDS-n/hyper. In the MDS-h group, 56.52% were male with a mean age of 57.0 ± 20.3 years, 53.85% were classified as intermediate risk, and 25.64% as low/very low risk according to the Revised International Prognostic Scoring System (IPSS-R). A total of 62.32% received grafts from HLA-matched related donors; 55.07% received peripheral blood stem cells as the graft source; 68.12% underwent myeloablative conditioning; 31.88% died; 75.36% developed post-transplantation complications, including 56.52% with infections, 50% with acute graft-versus-host disease (GVHD), and 28.85% with chronic GVHD; and 1.75% relapsed. Compared with patients with MDS-n/hyper, those with MDS-h were more frequently younger than 65 years (P = .042), classified in lower or intermediate IPSS-R risk categories (P = .017), were untreated prior to HCT (P = .0001), were more likely to receive reduced-intensity conditioning (P = .030), and exhibited lower relapse rates (P = .023). At 5 years, patients with MDS-h demonstrated significantly improved progression-free survival (PFS) after HCT compared with MDS-n/hyper (HR = 0.63; 95% CI: 0.40-0.99; P = .046). Overall survival (OS) and nonrelapse mortality (NRM) did not differ significantly between groups (P = .070 and P = .392, respectively). In univariate analysis, IPSS-R very high-risk was associated with increased mortality (HR = 2.18; 95% CI: 1.33-3.59; P = .002). In multivariable analysis, male sex (HR = 1.36; 95% CI: 1.00-1.85; P = .047) and IPSS-R very high risk (HR = 2.85; 95% CI: 1.69-4.81; P < .001) remained independent predictors of worse survival, whereas MDS-h was not associated with mortality.

In Latin America, MDS-h patients exhibited distinct and more favorable clinical and transplant-related characteristics, including younger age (<65 years), lower or intermediate IPSS-R risk, reduced relapse incidence, and reduced disease progression compared with MDS-n/hyper.