Characteristics and Outcomes of Adolescents (15–18 Years) with Chronic Myelogenous Leukemia (CML) in Chronic Phase: The Experience of the International Registry of Childhood CML ^†

Background: Chronic myeloid leukemia (CML) is a rare disease in children and adolescents. Discrepancies have been reported regarding the outcomes of adolescents, most of whom have been studied with younger or older patients not separately. Methods: The International Registry of Pediatric CML (I-CML-Ped Study) retrospectively and prospectively enrolled 614 patients less than 18 years old. Data from adolescents (15–18 years) with CML in chronic phase (CML-CP) were analyzed and compared to data from children less than 15 years old enrolled during the same period. Results: In total, 132 out of 144 adolescents presented with CML-CP: palpable spleen was reported in 67%, and the median leukocyte count was 181 G/L [interquartile range, 70–327]. Responses to treatment and outcome were analyzed in 124 adolescents with imatinib as first-line treatment: the cumulative incidence of major molecular responses (MMR) at months 12 and 36 was 33.4% (95% confidence interval CI, 24.9–41.9) and 79.8% (95% CI, 71.8–87.7), respectively. With a median follow-up of 4 years (95% CI: 3.5–4.9), 49 (40%) of these 124 patients were switched to another treatment, 11 (9%) patients progressed to the advanced phase, and the five-year overall survival rate was 95.2% (95% CI, 90.8–99.9%). We did not find significant statistical differences between these adolescents and younger children receiving imatinib in terms of response (complete cytogenetic response, MMR) and outcome (progression-free survival, overall survival). Conclusions: Response to treatment and outcomes in adolescents with CML-CP in the tyrosine kinase inhibitor era are satisfying without statistically significant difference from results observed in younger children.