A Risk Model Using Refined Disease Risk Index and 1-Month NK-Cell Count for Relapse in Children and Adults with...

To assess transplant outcomes after umbilical cord blood transplantation (UCBT) in patients with T-cell acute lymphoblastic leukemia/lymphoblastic lymphoma (T-ALL/LBL) and identify factors associated with relapse.

We retrospectively analyzed 105 patients with T-ALL/LBL (age, 2-53 years), who underwent single-unit UCBT as their first transplant at our center between January 2014 and June 2024. Transplant outcomes were assessed in the overall cohort. Relapse-associated factors were identified using Fine-Gray competing-risk regression in the subgroup with available 1-month peripheral blood natural killer (NK) cell measurements (58/105, 55.2%). The 1-month NK-cell count was dichotomized based on the median number in the analyzed cohort. A simplified risk score was derived from the final multivariable model. Model performance was assessed using time-dependent area under the curve (AUC) and calibration analysis.

In the overall cohort, the 3-year overall survival, progression-free survival, and GVHD-free relapse-free survival were 57.3% (95% CI, 46.9-66.4%), 54.9% (95% CI, 44.9-63.9%), and 49.3% (95% CI, 39.5-58.5%), respectively, and the 3-year cumulative incidence of relapse was 34.5% (95% CI, 25.5-43.6%). In the NK-measured subgroup, multivariable Fine-Gray analysis identified high refined Disease Risk Index (R-DRI) (sHR, 4.561; 95% CI, 1.662-12.51; P = 0.003) and low 1-month NK-cell count (< 0.165 × 10⁹/L) (sHR, 6.175; 95% CI, 1.711-22.280; P = 0.005) as independent factors associated with relapse. A 2-point score stratified patients into low-, intermediate-, and high-risk groups with 3-year relapse incidences of 0, 43.5% (95% CI, 23.3-62.1%), and 89.7% (95% CI, 48.6-98.4%), respectively (P < 0.001). The apparent 3-year AUC was 0.539 (95% CI, 0.255-0.823), and the optimism-corrected AUC was 0.523.

Relapse remains a major cause of treatment failure after UCBT in T-ALL/LBL. High R-DRI and low 1-month NK-cell count were independently associated with relapse and allowed apparent risk stratification in the development cohort. This exploratory 2-factor model may provide a basis for future studies of relapse assessment incorporating early immune recovery.