Combined use of WT1 and flow cytometry monitoring can promote sensitivity of predicting relapse after allogeneic HSCT without affecting specificity

Either WT1 or leukemia-associated aberrant immune phenotypes (LAIPs) was one of the minimal residual disease (MRD) parameters used to predict leukemia relapse after allogeneic hematopoietic stem cell transplantation (allo-HSCT). We first evaluated the clinical value of various positive MRD standards for accurately indicating relapse based on WT1 and FCM data in adult patients with acute leukemia (AL). In total, 824 AL patients treated with allo-HSCT were enrolled in this study. We compared the sensitivity and specificity of diverse, multiple-criteria MRD prognostic standards based on WT1 and FCM assays. Higher sensitivity was achieved without a loss of specificity when MRDco+, which was defined as two consecutive WT1_0.6+ or FCM+ or both WT1_0.6+ and FCM+ in the same sample within a year posttransplantation, was used as the positive MRD standard. Similar results were observed, even in 484 patients who had both abnormal WT1 and LAIPs values before transplant. A multivariate analysis showed that MRDco+ was an independent risk factor for leukemia relapse after transplant in both acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL). The combined use of FCM and WT1 monitoring could distinguish between patients with low and high risks of relapse. Various positive MRD standards were useful for guiding intervention.