High frequency of intermediate and poor risk copy number abnormalities in pediatric cohort of B-ALL correlate with high MRD post induction.

Copy number abnormalities (CNAs) and recurrent fusion transcripts are important genetic events which define and prognosticate B-Cell Acute Lymphoblastic Leukemia (B-ALL). We evaluated CNAs and fusion transcripts in 67 pediatric B-ALL cases and correlated the data with standard risk factors and early treatment outcome parameters. Common fusion transcripts ETV6-RUNX1, E2A-PBX, BCR-ABL1 and MLL-AF4 were examined by RT-PCR and noted in 15%, 15%, 13% and 1.4% of all cases respectively. CNAs in IKZF1, PAX5, EBF1, BTG1, RB1, CDKN2A/B and genes from PAR1 region viz., CSF2RA, IL3RA,P2RY8, SHOX region and CRLF2 were analyzed by multiplex ligation dependent probe amplification assay and were detected in 70% (47/67) of cases, with predominantly deletions in CDKN2A/B (36%), PAX5 (18%) and IKZF1 (16%). A statistically significant association of intermediate/poor risk CNAs was noted with high WBC count (p = 0.001), NCI group (p = 0.02) and minimal residual disease at Day35 (p < 0.0001). IKZF1 and CDKN2A/B deletion revealed poor EFS of 56% at 24 months as compared to EFS of 80% in rest of the cases (p = 0.05) suggesting their potential role in early risk stratification.