Prognostic Value of Molecular Genetic Measurable Residual Disease (MRD) Monitoring in Pediatric Acute Myeloid Leukemia Expressing KMT2A::MLLT10

Objectives: Pediatric AML with KMT2A::MLLT10 accounts for 10%-15% of KMT2A-rearranged AML and is associated with poor prognosis. Lately, the assessment of measurable residual disease (MRD) by reverse transcription quantitative polymerase chain reaction (RT-qPCR) has become an important tool for disease management; however, in the pediatric setting, it lacks standardized protocols. Therefore, we investigated the prognostic relevance of MRD monitoring by RT-qPCR during high-dose polychemotherapy in pediatric patients with AML expressing KMT2A::MLLT10. Methods: Using RNA sequencing, we determined the fusion breakpoints and designed RT-qPCR assays for MRD monitoring. Bone marrow samples collected from 41 patients, who were treated in the AML-BFM or AIEOP study, were analyzed for MRD by RT-qPCR. Results: MRD positivity after the second treatment course resulted in a significantly worse probability of overall survival (pOS) compared to MRD negative patients (33.3% ± 19.2% vs. 80.6% ± 7.8%, p = 0.032). Moreover, the probability of event-free survival (pEFS) (16.7% ± 15.2% vs. 76.9% ± 8.3%, p = 0.003) and cumulative incidence of relapse (CIR) (83.3% ± 40.8% vs. 19.2% ± 40.2%, p = 0.001) were significantly worse for patients in complete morphologic remission who remained MRD positive after the second treatment course. Conclusion: Thus, MRD monitoring enables the identification of a subgroup of pediatric patients with AML carrying KMT2A::MLLT10 in complete morphologic remission with a dismal prognosis despite the current intensive therapy regimen.