Role of WT1 in Measurable Residual Disease Follow-Up in the Post Allogeneic Stem Cell Transplant Setting

<b>Objectives</b>: The Wilms' tumor gene 1 (WT1) plays a critical role in cell development and the regulation of essential genes involved in cell growth and metabolism. In the context of hematopoietic tumors, including acute myeloid leukemia (AML), WT1 has been identified as a potential marker for measurable residual disease (MRD) assessment. Relapse after allogeneic hematopoietic stem cell transplantation (allo-SCT) remains a significant challenge in AML treatment, highlighting the importance of MRD monitoring for risk stratification and treatment decisions. This study aimed to investigate the clinical significance of WT1 as a molecular marker for MRD and its correlation with chimerism in AML patients post-allo-SCT setting. <b>Methods:</b> We have included 58 patients with WT1-expression-positive acute myeloid leukemia (AML) who received allo-SCT in our center between 2016-2022. The exclusion criteria are as follows: not having WT1 polymerase chain reaction (PCR) measurement at diagnosis, not receiving allo-SCT, and not having a serial measurement of WT1 post-transplant. Pre- and post-transplant assessments were made with flow cytometry, WT1 PCR, and bone marrow morphological evaluations. Statistical analyses were carried out to explore correlations between WT1 levels, MRD markers, and chimerism post-transplantation. <b>Results:</b> We found that WT1 had a significant correlation with flow cytometry and bone marrow morphological evaluation, but not with chimerism. Interestingly, high WT1 expressors exhibited a more robust correlation with chimerism compared to the general cohort. The negative predictive value for post-allo-SCT relapse was 91.8% for the whole WT1 cohort; for high WT1 expressors, it was similar, at 87.5%. The negative predictive value for post-allo-SCT relapse was high for the whole WT1 cohort; for high WT1 expressors, it was similar. The WT1 MRD assay showed a high negative predictive value for post-allo-SCT relapse, consistent across both the entire cohort (91.8%) and high WT1 expressors (87.5%). <b>Conclusions:</b> WT1 expression levels may serve as a valuable ancillary marker in MRD assessment and relapse prediction post-allo-SCT in AML patients, particularly for those lacking specific fusion genes or mutations. However, further large-scale, controlled studies are needed to standardize WT1 MRD assays and establish clear guidelines for their clinical application.