THE SIGNIFICANCE OF THE BCR::ABL1 BIOMARKER IN THE DIAGNOSIS AND TREATMENT MONITORING OF CHRONIC MYELOID LEUKEMIA: A NARRATIVE REVIEW

Abstract

Abstract

Chronic myeloid leukemia is defined by the presence of the BCR::ABL1 fusion, which plays a central role in disease pathogenesis, diagnosis, treatment selection, and molecular monitoring. This narrative review aimed to summarize the current clinical significance of BCR::ABL1, with particular emphasis on diagnostic methods, assessment of response to tyrosine kinase inhibitors, mechanisms of resistance, and treatment-free remission. A literature search was conducted using PubMed and Google Scholar, focusing primarily on English-language guidelines, review articles, and clinically relevant studies published between 2015 and 2025, while also including earlier landmark publications. The review shows that cytogenetic analysis, fluorescence in situ hybridization, and reverse-transcription polymerase chain reaction provide complementary diagnostic information. Serial RT-qPCR measurement of BCR::ABL1 on the International Scale remains the standard method for assessing the depth and kinetics of molecular response. Interpretation should consider previous results, treatment adherence, dose modifications, assay variability, and the overall clinical context. Detection of kinase-domain mutations, particularly T315I, may explain treatment resistance and guide subsequent TKI selection. Targeted next-generation sequencing and digital PCR may improve the detection of resistant subclones and low-level residual disease, but their findings should not be used as isolated treatment criteria. Overall, accurate and standardized BCR::ABL1 monitoring remains essential for individualized CML management, while further research is needed to validate additional prognostic markers and improve prediction of treatment-free remission.