Cytogenetic Risk Profile of Paediatric Acute Lymphoblastic Leukaemia in a Single-Centre Cohort From Western India: Frequency of BCR::ABL1, Hypodiploidy and Co-Occurring Chromosomal Abnormalities and their Association with Induction Response

Background: Risk-adapted therapy for childhood acute lymphoblastic leukaemia (ALL) rests on cytogenetic distributions described largely in Western trial cohorts. Indian series report variable lesion frequencies, but most rely on G-banding alone and seldom record co-occurring abnormalities. We described the cytogenetic risk profile of paediatric ALL at a single centre in western India and examined its association with induction response.Methods: Single-centre retrospective cohort study (December 2023 to June 2025). Fifty-four children aged 16 years or younger with newly diagnosed ALL underwent G-banded karyotyping and interphase fluorescence in situ hybridisation (FISH) for ETV6::RUNX1, BCR::ABL1 and KMT2A rearrangement. Co-occurring abnormalities were recorded as composite findings, and children were assigned to good, intermediate or poor cytogenetic-risk groups by a pre-specified lesion-based rule applied without reference to outcome. Associations with end-of-induction morphological response were examined by Fisher exact test; proportions are given with 95% confidence intervals (CI).Results: Cytogenetic risk was good in 22 (40.7%; 95% CI 28.7–54.0), intermediate in 15 (27.8%; 17.6–40.9) and poor in 17 (31.5%; 20.7–44.7). BCR::ABL1 was detected in 8 (14.8%), hypodiploidy in 7 (13.0%), KMT2A rearrangement in 5 (9.3%) and t(1;19) in 7 (13.0%); 7 (13.0%) had no detectable abnormality. Thirteen of 16 high-hyperdiploid cases (81%) had a co-detected additional abnormality, most often ETV6::RUNX1. Complete remission was achieved by 19/22 (86.4%), 12/15 (80.0%) and 7/17 (41.2%) children in the good-, intermediate- and poor-risk groups (p<0.001, unadjusted); induction failure occurred in 1, 0 and 9, including six of seven hypodiploid children, whereas both KMT2A-rearranged T-ALL cases achieved remission. Conclusion: BCR::ABL1-positive and hypodiploid ALL were more frequent than in published Western reference ranges,co-occurring abnormalities were common, and poor-risk cytogenetics, hypodiploidy in particular, was strongly associatedwith induction failure. These single-centre observations are hypothesis-generating and require confirmation in multicentrestudies with uniform treatment, extended genomic testing and survival endpoints.