Adjuvant Maintenance Larotrectinib Therapy in 2 Children With NTRK Fusion-positive High-grade Cancers.

Treatment-related morbidity drives research to identify targetable lesions in children with cancer. Neurotrophic tropomyosin receptor kinase (NTRK) alterations occur in ~1% of pediatric solid tumors. Early phase pediatric trials involving the NTRK inhibitor treatment for progressive NTRK-mutated cancers show promising results. The authors describe the adjuvant maintenance larotrectinib treatment after definitive surgical resection in 2 toddlers with NTRK fusion-positive malignancies (ETV6-NTRK3 fusion-positive undifferentiated embryonal sarcoma of the kidney and NACC2-NTRK2 fusion-positive anaplastic astrocytoma). Both are alive, in remission, developing normally and tolerating larotrectinib 15 months later, thus extending the NTRK inhibitor therapeutic spectrum by describing the adjuvant maintenance larotrectinib treatment in children with NTRK fusion-positive cancers associated with high recurrences.