Laboratory Concordance and Prognostic Impact of 10‐Color Flow Cytometry and Next‐Generation Sequencing‐Based Immunoglobulin Gene Assay for Measurable Residual Disease Monitoring in Adult B‐Cell Acute Lymphoblastic Leukemia: A Multicenter Study From Thai Acute Leukemia Working Group ( TALWG )

Abstract

ABSTRACT Aims Measurable residual disease (MRD) is a key prognostic marker for patient survival. This study evaluated concordance between 10‐color flow cytometry and next‐generation sequencing (NGS)–based immunoglobulin heavy chain (IGH) gene assays for MRD detection and to assess prognostic significance in adult B‐cell acute lymphoblastic leukemia (B‐ALL). Methods This multicenter prospective study enrolled 51 patients with newly diagnosed B‐ALL. Bone marrow samples were obtained at diagnosis, post‐induction (1 month), and post–early consolidation (3 months). Flow cytometry and NGS‐IGH were performed at three timepoints to assess MRD B‐ALL. Results Patients were classified as high risk according to white blood cell count and cytogenetic features in 37.3% and 64.7% of patients, respectively. Treatment protocols included pediatric‐inspired regimens (41.2%), adult‐ALL protocols (52.9%), and low‐intensity chemotherapy. All 16 Philadelphia chromosome–positive patients received tyrosine kinase inhibitors. Twenty patients underwent allogeneic hematopoietic cell transplantation (HCT) in first complete remission (CR). Median relapse‐free survival (RFS) and overall survival were 19 and 39 months, respectively. MRD negativity at 3 months by either method correlated with significantly superior RFS. Allogeneic HCT also conferred RFS benefit. MRD positive patients without HCT had the worst RFS. Flow cytometry MRD positivity at 3 months independently predicted inferior RFS (HR 3.81; 95% CI 1.01–14.43). The overall concordance between flow cytometry and NGS was 80.7%. Conclusion MRD positivity at 3 months post‐treatment strongly predicted relapse, supporting its use to guide therapeutic modifications of B‐ALL. Apart from NGS‐based IGH clonality assays, 10‐color flow cytometry offers an alternative in resource‐limited settings.