Early Peripheral Blood WT1 Expression Predicts Relapse After Allogeneic Hematopoietic Stem Cell Transplantation in Acute Myeloid Leukemia.

Relapse remains the leading cause of treatment failure after allogeneic hematopoietic stem cell transplantation (allo-HSCT) in acute myeloid leukemia (AML). Early identification of patients at increased post-transplant relapse risk is essential to enable intensified surveillance and pre-emptive therapeutic strategies. Wilms' tumor 1 (WT1) is overexpressed in most AML cases and represents a broadly applicable molecular marker; however, its utility as a peripheral blood (PB) measurable residual disease (MRD) marker after allo-HSCT remains incompletely defined. In this prospective multicenter cohort study, 43 adults with AML in complete remission underwent allo-HSCT between 2021 and 2023. WT1 expression in PB was quantified using standardized real-time quantitative PCR before transplantation (WT1_pre) and at day +30 (WT1_30). Receiver operating characteristic analysis identified an optimal threshold for relapse prediction. A WT1 cutoff of ≥3 copies/104ABL discriminated relapse risk. WT1_30 demonstrated strong prognostic performance (AUC 0.79; p = 0.005), whereas WT1_pre showed more modest predictive value (AUC 0.69; p = 0.037). Patients with WT1_30 ≥ 3 had inferior 12-month progression-free survival compared with those with WT1_30 < 3 (52.9% vs. 90.9%, p = 0.0059) and a higher 12-month cumulative incidence of relapse (31% vs. 9%, p = 0.054). WT1_pre ≥ 3 was also associated with inferior progression-free and overall survival (both p = 0.0008). Relapsed patients had significantly higher WT1_30 levels than non-relapsed patients (median 5.0 vs. 2.0 copies/104 ABL; p = 0.018). Peripheral blood WT1 expression, particularly at day +30, is associated with an increased relapse risk after allo-HSCT in AML and may support early post-transplant risk stratification. The identified cutoff should be considered exploratory and requires validation in larger independent cohorts.