BCR-ABL1 and CD66c exhibit high concordance in minimal residual disease detection of adult B-acute lymphoblastic leukemia.

OBJECTIVE: To investigate the relationship between surface expression of CD66c and the breakpoint cluster region-Abelson (BCR-ABL1) fusion gene in B-acute lymphoblastic leukemia (B-ALL) at primary diagnosis, and their concordance during minimal residual disease (MRD) monitoring. METHODS: Bone marrow biopsies were collected from newly diagnosed B-ALL patients (n = 43) between September 2011 and September 2014. Karyotyping was used to detect Philadelphia chromosome (Ph), and fluorescence in situ hybridization (FISH) and reverse transcription-polymerase chain reaction (RT-PCR) were used to detect BCR-ABL1 fusion gene. Immunophenotyping was performed by flow cytometry for leukemia. Patients with both CD66c expression and BCR-ABL1 were further assessed for MRD during treatment. RESULTS: Overall, 26/43 (60.5%) B-ALL patients were positive for BCR-ABL1 fusion gene expression, and all Ph positive cases (17/43; 39.5%) expressed BCR-ABL1 and CD66c. CD66c was expressed at significantly higher levels in BCR-ABL1 positive than negative patients (24/26, 92.3% vs. 11/17, 64.7%; P = 0.042), and furthermore, in all Ph positive cases (17/17, 100% vs. 18/26, 69.2%; P = 0.014). When BCR-ABL1 was set as the gold standard for the presence or absence of MRD after treatment, both CD66c alone and the MRD panel including CD66c demonstrated high diagnostic performance for the detection of MRD, with values of area under the receptor operation curve (ROC) of 0.881 vs. 0.891 respectively. CONCLUSIONS: The stable expression pattern of CD66c has noteworthy clinical value in B-ALL not only in the recognition of abnormal leukemia cells at primary diagnosis but also in monitoring of MRD during the treatment, especially in patients without definitely cytogenetic or molecular abnormal, and thus, warrants further investigation as a routine clinical marker for MRD detection by flow cytometry.