Children with chronic-phase chronic myeloid leukemia: characteristics and outcomes from the International Registry of Childhood CML

Five hundred and thirty-five patients (median age 12.2 years; range, 8 months to 18 years; N=303 males, N=232 females) diagnosed with chronic myeloid leukemia (CML) in chronic phase were registered in the International Registry of Childhood CML (clinicaltrials gov. Identifier: NCT01281735). Clinical signs of leukostasis or bleeding were observed in 16.5% and 20% of the patients, respectively. The spleen was palpable in 76% of patients with a median of 9 cm (range, 1-32) below the costal margin. The median leukocyte count was 222x109/L (interquartile range, 95-353). First-line therapy consisted of imatinib in 482 children. Among them, 40% remained on imatinib with a median follow-up 3.8 years (95% confidence interval [CI]: 3.2- 4.3 years); 3.1% died and 3.9% progressed to advanced-phase disease. The overall survival rate at 36 months was 97.4% (95% CI: 95-99%). Progression-free survival rate at 3-years was 97.1% (95% CI: 94.9-99.2%), 91.7% (95% CI:84.5-98.3%) and 72.0% (95% CI: 59-87.9%) in the Eutos Long-Term Survival (ELTS) low-, intermediate-, and high-risk group, respectively (P log rank <0.001). Pediatric CML is characterized by bulky disease (large splenomegaly, high leukocyte counts) and the ELTS score can identify children with the poorest outcome.