Impact of Residual Disease Localization Before Allogeneic Hematopoietic Stem Cell Transplantation on Outcomes in Adult T-Cell Leukemia-Lymphoma.

Allogeneic hematopoietic stem cell transplantation (allo-HCT) is the only curative approach for adult T-cell leukemia-lymphoma (ATL). However, preventing post-transplant relapse remains challenging. While pre-transplant disease status is known to be associated with post-transplant outcomes, the impact of residual disease (RD) localization at the time of allo-HCT has not been well described. In this retrospective study of 33 patients with aggressive ATL who underwent allo-HCT, patients were classified into two risk groups based on RD sites: a low-risk group (no lymph node [LN] or extranodal [EN] disease, regardless of the presence of peripheral blood disease) and a high-risk group (presence of LN and/or EN disease). The low-risk group had significantly superior overall survival (OS) and progression-free survival (PFS) compared to the high-risk group, with longer median survival times (OS: 1953 vs. 245 days; PFS: 1177.5 vs. 72 days) and higher 2-year survival rates (OS: 65.0% vs. 11.3%; PFS: 50.0% vs. 8.3%) (p = 0.012 and p = 0.013, respectively). Furthermore, even among patients who had not achieved complete response, RD localization stratified the survival outcomes: the 2-year OS and PFS were 75.0% and 75.0% in the low-risk group, compared with 11.3% and 8.3% in the high-risk group, respectively. In conclusion, RD localization at the time of allo-HCT is a novel prognostic factor, highlighting the need for tailored pre-transplant management for ATL.