Optimizing cord blood unit selection to improve survival after single‐unit unrelated cord blood transplantation for adult myelodysplastic syndrome

Summary Unrelated cord blood transplantation (CBT) is an important alternative donor option for adult patients with myelodysplastic syndrome (MDS); however, the prognostic significance of cord blood unit characteristics following CBT remains unclear and may vary according to disease risk. We conducted a nationwide retrospective study of 1767 adult patients with MDS who underwent first single‐unit CBT between 1999 and 2023, including 529 patients with low‐risk and 1238 with high‐risk disease at transplantation. Cord blood unit characteristics were not significantly associated with disease‐free survival (DFS) in patients with low‐risk MDS. In contrast, in patients with high‐risk MDS, higher cryopreserved cluster of differentiation (CD)34 + cell dose and higher colony‐forming unit–granulocyte/macrophage dose were associated with improved DFS, whereas human leucocyte antigen (HLA) serological one‐locus mismatch and female‐to‐male donor–recipient sex mismatch were independently associated with inferior DFS. Restricted cubic spline Cox regression demonstrated a significant non‐linear association between CD34 + cell dose and DFS, as well as relapse, in high‐risk MDS. These findings demonstrate that the prognostic impact of cord blood unit characteristics after single‐unit CBT differs according to MDS risk status and support a risk‐adapted approach to cord blood unit selection, particularly for patients with high‐risk MDS.