B-327 Measurable Residual Disease Monitoring at Acute Myeloid Leukemia Based on Laboratory Data

Background Measurable Residual Disease (MRD) is an important biomarker at Acute Myeloid Leukemia (AML) monitoring, prognosis, predictor of recurrence and guidance of treatment decisions. Different techniques were available to MRD analysis, such as: RT-qPCR/digital droplet PCR, Next Generation Sequency and Multiparametric Flow Cytometry (MFC), through immunophenotyping of abnormal cell population. The MFC is an essential tool for studying the cell lineages involved in AML. The LAIP characterization (Leukemia-associated immunophenotypes) at the diagnosis moment is critical to establish the best strategy reproducible to the MRD study. This study aimed to analyze the immunophenotyping data from patients with AML diagnoses, based on laboratory MRD exams. Methods A retrospective analysis was performed using MRD immunophenotyping data from bone marrow (BM) and peripheral blood (PB) samples of patients diagnosed with AML in the internal database of a clinical laboratory in São Paulo, Brazil, between September 2023 and November 2024. MRD analyses were performed by MFC using an internal standardized marker panel. The analyses strategies used were maturation different from normal (DfN) and LAIP. Data analysis included: age, gender, number of patients, test results, sample type and LAIP frequency. Results MRD tests were performed for 62 patients, of which 56% (35/62) are female, with the highest incidence in those = 50 years, accounting for 28 (45.2%) cases. Of these, 42 patients have a diagnosis analyzed in our service. Each patient had between one and seven MRD tests during treatment monitoring, totaling 146 MRDs analyzed. The gold standard material for MRD testing is BM; however, 9.6% (14/146) of the MRDs were performed using PB. Of the 62 patients, 48.4% (30/62) were negative on the first MRD, 9.7% (6/62) on the second, 1.6% (1/62) on the third, and 1.6% (1/62) on the fourth, highlighting a group of patients who respond to treatment. 21% (13/62) of the patients tested positive for MRD, even after one to four negative tests, with blast percentages ranging from 0.09% to 19.04%, indicating a group of patients with relapse disease. 17.7% (11/62) of the patients remained with positive MRD results, demonstrating a group of patients possibly refractory disease. About the LAIPs of lineage infidelity, they were found in 40.4% (76/188) of the cases, considering diagnosis and follow-up, with frequencies of CD123 (41.9%), CD7 (25.6%), CD56 (19.8%), CD2 (7%), and CD19 (5.8%). In an analysis focused on patients, 31 (50%) patients presented at least one type of LAIPs. Conclusion MRD analysis is essential for monitoring AML and has been employed in clinical trials of new agents and emerging therapies for AML. Among the techniques available for MRD research, immunophenotyping by MFC has advantages such as broad applicability, accessibility, turnaround time, specificity, and lower cost comparable to other techniques.