Graft CD8 T‐cell‐based risk system predicts survival in antithymocyte globulin‐based myeloablative haploidentical peripheral blood stem cell transplantation

Abstract

ObjectiveThis study investigated the cellular composition of peripheral blood grafts for anti‐thymocyte globulin (ATG)‐based myeloablative haploidentical haematopoietic stem cell transplantation (haplo‐HSCT).MethodsClinical characteristics were retrospectively evaluated in a training cohort with ATG‐based myeloablative haplo‐HSCT between January 2016 and February 2020 and confirmed in a validation cohort between March 2020 and June 2021.ResultsA higher dose of graft CD8+ T cells (≥ 0.85 × 108 kg−1) was significantly improved overall survival (OS; hazard ratio [HR], 1.750; P = 0.002) and disease‐free survival (DFS; HR, 1.751; P < 0.001) in the training cohort, according to multivariate Cox regression analysis. Higher doses of mononuclear cells (MNCs) demonstrated better OS (HR, 1.517; P = 0.038) and DFS (HR, 1.532; P = 0.027). Older patient age (> 46 years), older donor age (≥ 50 years) and a higher refined disease risk index (rDRI) were also related to OS. A graft CD8+ T‐cell risk system based on graft CD8+ T‐cell dose, donor age and rDRI was constructed using a nomogram model after LASSO Cox regression analysis. It showed acceptable discrimination, with a C‐index of 0.62 and 0.63, respectively. Graft CD8+ T‐cell dose was negatively correlated with donor age (P < 0.001) and positively correlated with a higher lymphocyte percentage in the peripheral blood before mobilisation (P < 0.001).ConclusionA higher CD8+ T‐cell dose in peripheral blood‐derived grafts improves patients' survival with ATG‐based myeloablative haplo‐HSCT. Younger donors with higher lymphocyte percentages improved patients' survival with an intermediate rDRI risk.