Long-term outcomes of chronic myeloid leukemia in children and adolescents - Real world data from a single-institute in Taiwan.

Background/purpose: Tyrosine kinase inhibitors (TKIs) have revolutionized chronic myeloid leukemia (CML) treatment, yet long-term pediatric outcomes and growth effects remain limited. This study describes the long-term efficacy and growth impact of TKIs in children and adolescents with CML.

Methods: We retrospectively reviewed 14 pediatric CML patients treated with TKIs at our institute. The cohort's molecular responses and growth velocities were evaluated over a median follow-up of 15.9 years. MR4.5 was defined as BCR-ABL1/ABL ratio <0.0032%. Cumulative MR4.5 rates, time to response, and growth impacts were described among first- and second-generation TKIs.

Results: All patients achieved MR4.5, with second-generation TKIs showing faster responses than imatinib. Growth deceleration was observed in patients initiating TKIs at prepubertal ages, regardless of TKI type. Among four patients who discontinued TKIs, three maintained treatment-free remission (TFR) for a median of 4.0 years. Adverse events from second-generation TKIs led to treatment switches in four among eleven patients (36%).

Conclusion: This study shows the sustained efficacy of TKIs in achieving MR4.5 in pediatric CML, with second-generation TKIs providing faster responses. Growth retardation remains a concern for TKI treatment. TKI discontinuation in pediatric CML may be feasible and crucial for shortening TKI exposure and optimizing long-term growth outcomes in prepubertal patients.