Long-term outcome of tyrosine kinase inhibitor treatment in children and adolescents with newly diagnosed chronic myeloid leukemia in chronic phase

Chronic myeloid leukemia(CML)is relatively rare in children,with an average annual incidence of 0.6 to 1.0 case per million in children<15 years and 2.2 cases per million in adolescents aged 15 to 19 years,accounting for 2%to 3%and 9%of all newly diagnosed leukemia cases in these two age groups,respectively.[1]Imatinib mesylate(IM)was approved by the US Food and Drug Administration(FDA)in 2003 and has gradually replaced hematopoietic stem cell transplantation(HSCT)as the first-line treatment for pediatric patients with chronic-phase CML(CML-CP).[2]However,IM treatment is discontinued in 25%to 29%of pediatric patients with CML-CP because of drug resistance or intolerance.[3]For such patients,second-generation tyrosine kinase inhibitors(2G-TKIs),including dasatinib and nilotinib,were approved by the FDA as first-and second-line therapies in 2017 and 2018,respectively.[2]However,given the rarity of this neoplasm and the lack of clinical trial data,treatments for pediatric CML follow the recommended adult regimen,and little is known about the long-term efficacy and safety of these treatments in children and adolescents.[2]Furthermore,there are few reports detailing the sequential use of IM as first-line treatment followed by 2G-TKIs as second-line therapy in Chinese pediatric patients with CML.Therefore,there is a strong need to investigate the long-term effects of IM treatment in a large cohort of Chinese pediatric patients.In this report,we retrospectively analyzed the long-term follow-up results of 58 pediatric patients with CML-CP treated with IM as first-line therapy and 2G-TKIs as second-line therapy in a single South China center.