Significance of Pre- and Posttransplant Minimal Residual Disease on Transplant Outcomes in Core-Binding Factor Acute Myeloid Leukemia.

Background: Polymerase chain reaction (PCR)-based Minimal residual disease (MRD) detection is commonly used for core-binding factor acute myeloid leukemia (CBF-AML), but its interpretation in the context of allogeneic hematopoietic stem cell transplantation (allo-HSCT) remains under discussion.

Method: Using Kyoto Stem Cell Transplantation Group registry data, we included 96 patients who underwent allo-HSCT between 2000 and 2019 for CBF-AML.

Results: To assess MRD, quantitative PCR with GAPDH control was most used. As for pretransplant MRD, 2-year overall survival (OS) and relapse-free survival (RFS) of the weak positive group (50-200 copy/μgRNA) were 66.5% and 67.2%, and these were as unfavorable as those of the strong positive group (> 200 copy/μgRNA, OS; 64.3%, RFS; 54.5%) compared to the negative group (OS; 100%, RFS; 93.3%). In contrast, as regards posttransplant MRD, 2-year OS of patients with lower maximum MRD during approximately half a year post-transplantation period (50-350 copy/μgRNA, 81.5%) was comparable to that of MRD-negative patients (84.5%). In multivariate analysis, higher maximum MRD (> 350 copy/μgRNA) was a significant unfavorable factor toward OS (hazard ratio: 6.3, p = 0.002) compared to negative MRD.

Conclusions: The interpretation of posttransplant MRD positivity should be approached with caution, particularly in cases with low-level positivity as it might diminish over time.