Objective:To investigate the consistency and sensitivity of minimal residual disease (MRD) detected by multicolor flow cytometry (FCM) and real-time quantitative polymerase chain reaction (RQ-PCR) in patients with acute myeloid leukemia (AML) accompanied by monocytic differentiation after allogeneic hematopoietic stem cell transplantation (allo-HSCT).Methods:A retrospective case series study was conducted. A total of 218 patients diagnosed with AML accompanied by monocytic differentiation who underwent allo-HSCT in Peking University People's Hospital between January 2017 and December 2021 were included. MRD was detected by using bone marrow FCM and RQ-PCR at predefined intervals (at 1-, 2-, 3-, 4.5-, 6-, 9-, and 12-month before and after transplantation). Patients were grouped based on AML-related specific genes, and dynamic changes in MRD results detected by FCM and RQ-PCR after transplantation were analyzed to evaluate the correlation with post-transplant relapse.Results:A total of 218 enrolled patients included 114 males and 106 females, with the median age of 32 years (1-65 years). The median follow-up duration was 218 d (21-1 541 d). Hematologic relapse occurred in 26 patients (12.7%), with a median relapse time of 272 d (83-934 d); 35 patients (15.9%) died, including 15 (6.9%) due to leukemia relapse and 20 (9.2%) due to transplant-related mortality. Predictive markers for relapse included once WT1 positive (WT1+once), twice WT1 positive (WT1+twice), CBFβ::MYH11 fusion genes positive, mixed-lineage leukemia (MLL)-related fusion genes positive, AML1::ETO fusion genes positive, and once FCM positive (FCM+once), twice FCM positive (FCM+twice). The overall consistency rate between FCM and RQ-PCR for MRD detection in AML patients accompanied by monocytic differentiation after transplantation was 75.7% (165/218). The consistency rate of MRD detection results in WT1+once, WT1+ twice, MLL-related fusion gene positive, and NPM1 gene mutation positive with FCM was higher than the average value (>75.7%), while the consistency rate of MRD detection results in AML1::ETO and CBFβ::MYH11 fusion gene positive with FCM was lower than the average value (<75.7%). Notably, persistent low-level positivity without relapse after transplantation occurred in cases with WT1 (15 patients), NPM1 (2 patients), CBFβ::MYH11 (11 patients), or AML1::ETO (2 patients); in contrast, MLL-related fusion genes (particularly MLL::AF6 and MLL::AF9) positive after transplantation indicated relapse in patients. The sensitivity and specificity of RQ-PCR for MRD monitoring varied by genetic markers: WT1+once and WT1+twice (sensitivity: 66.7%, 50.0%; specificity: 84.5%, 91.1%, respectively), AML1::ETO (sensitivity: 100.0%; specificity: 50.0%), CBFβ::MYH11 (sensitivity: 100.0%; specificity: 58.6%), MLL-related fusion genes (sensitivity: 75.0%; specificity: 96.4%), and NPM1 (sensitivity: 75.0%; specificity: 91.7%).Conclusions:The sensitivity and specificity of AML-related genetic markers for recurrence prediction show differences. Discrepancies between RQ-PCR and FCM in MRD detection are notable in AML with monocytic differentiation after transplantation. FCM exhibits relatively lower sensitivity for MRD monitoring in this subtype, while RQ-PCR based on AML-related genes may compensate for FCM limitations.

Objective:This study aimed to observe the dynamic changes of NUP98::NSD1 expression before and after allogeneic hematopoietic stem cell transplantation (allo-HSCT) . Moreover, the clinical value of measurable residual disease (MRD) was analyzed.Methods:Sixteen AML patients who were diagnosed with the NUP98::NSD1 fusion gene and received allo-HSCT at Peking University People’s Hospital were included. The NUP98::NSD1 fusion gene and leukemia-associated immunophenotype (LAIP) were monitored before and after transplantation to evaluate their MRD status.Results:The median follow-up time for all patients was 526 days (139-1136 days) , with four patients (25.0%) experiencing hematological recurrence at a median of 474 days (283-607 days) after transplantation. Three patients (18.8%) died, two of whom (12.5%) died of leukemia recurrence. The median expression level of NUP98::NSD1 in newly diagnosed patients with complete data was 78.5% (18.9%-184.4%) at the time of initial diagnosis. The recurrence rate was higher in NUP98::NSD1-positive patients after transplantation, with 44.4% of patients experiencing recurrence, whereas no recurrence occurred in NUP98::NSD1-negative patients after transplantation. The area under the receiver operating characteristic curve predicted by the NUP98::NSD1 level after transplantation was 1.000 (95% confidence interval: 1.000-1.000, P=0.003) . Among the four patients with recurrence, NUP98::NSD1 was more sensitive than flow cytometry residual (FCM) and Wilms’ tumor gene 1 (WT1) . Conclusions:The NUP98::NSD1 fusion gene can be used to evaluate the MRD status of allo-HSCT. NUP98::NSD1-positive patients after transplantation have a high relapse rate and poor prognosis. NUP98::NSD1 was more sensitive than FCM and WT1 in predicting posttransplant relapse.