Comparative Outcomes for HLA-Matched Siblings, Mismatched, and Haploidentical Donors in Myelodisplastic Syndromes: Report from the Latin American Register

Introduction Allogeneic stem cell transplantation (allo-HSCT) remains the only curative treatment for Myelodisplastic Syndromes (MDS) and many factors may predict outcomes as cell source, conditioning regimen and donor type. Haploidentical HSCT is an alternative in the absence of an HLA-matched donors. In generall, clinical studies comparing recipient outcomes after allo-SCT with HID versus MSD or MUD in myeloid malignancies have suggested similar outcomes, with an overall survival (OS) between 40% and 80%, but few studies focused on the outcomes after allo-HSCT for MDS patients (excluding AML). Objective The aim of this study is to analyze the characteristics and survival outcomes of patients undergone to (HSCT) regarding donor type. Methods we compared the outcomes of 400 patients from the transplant registry of 32 centers in Latin America available at tmo.med.br website, during July 1988 to May 2023. Results The predominant donor type was matched sibling (MSD) (65%) followed by matched unrelated (MUD) (22,75%) and haploidentical (HID) (12,25%). Median recipient age at transplant slightly differed, with a higher median age of 46 years in the MSD group (p < 0.001). High/Very High risk R-IPSS category was more frequent in HID group (p=0,022). Pre-treatment was more frequent in MUD and HID groups (p<0,001), being Hypomethylating most commonly used in these groups while Chemotherapy was more frequent in MSD group. It was observed a higher prevalence of reduced intensity conditioning in HID group (p < 0.001) and myeloablative in the other groups. Chronic Graft Versus Host Disease (GVHD) was predominant in MSD group (p=0,006). Infections were observed in post HSCT with similar frequency in the groups (p=0,266), but CMV reactivation was higher in HID (p=0,033). The general frequency of death was 39,5% (n=158). The 5-years Overall Survival was 54.5%. It did not significantly differed regarding type of donors. In multivariable analysis, type of donor did not influenced outcomes of HSCT. Presence of treatment prior to HSCT and high risk R-IPSS stratification were the variables that independently had prognostic impact in outcomes of the procedure. Conclusion Despite some drawbacks regarding limited information, the study showed similar outcomes after allo-SCT with (HID). Even with a higher frequency of CMV reactivation, haploidentical HSCT did not influenced death and overall survival for MDS patients being a suitable alternative for HSCT. Prospective studies in MDS are needed to confirm results and elucidate questions pointed.