Impact of early molecular response in children with chronic myeloid leukemia treated in the French Glivec phase 4 study.

Studies in adults have shown that an early molecular response to imatinib predicts clinical outcome in chronic myeloid leukemia (CML). We investigated the impact of the BCR-ABL1 transcript level measured 3 months after starting imatinib in a cohort of 40 children with CML. Children with a BCR-ABL1/ABL ratio higher than 10% at 3 months after the start of imatinib had a larger spleen size and a higher white blood cell count compared with those with BCR-ABL1/ABL ≤10%. Children with BCR-ABL1/ABL ≤10% 3 months after starting imatinib had higher rates of complete cytogenetic response and major molecular response at 12 months compared with those with BCR-ABL1/ABL >10%. With a median follow-up of 71 months (range, 22-96 months), BCR-ABL1/ABL ≤10% correlated with better progression-free survival. Thus, early molecular response at 3 months predicts outcome in children treated with imatinib for CML. This trial was registered at www.clinicaltrials.gov as #NCT00845221.