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Molecularly targeted therapy with MEK inhibitors has been increasingly incorporated into the treatment of pediatric low-grade gliomas, but this promising therapy is associated with distinctive and specific toxicities. Understanding life-threatening MEK inhibitor toxicities and their management is critical to MEK inhibitor safety, especially among young children. This report describes severe hyponatremia associated with trametinib in an infant with progressive low-grade glioma without underlying endocrine dysfunction, which recurred despite significant dose reduction. Therapy with an alternative MEK inhibitor, binimetinib, provided excellent tumor response without hyponatremia, suggesting that some toxicities may be avoided by changing MEK inhibitor agents within the same class.

Pediatric cancer patients have a high prevalence of vitamin D deficiency. Children and young adults with acute lymphoblastic leukemia are at high risk for associated poor bone outcomes due to contributing effects of chemotherapy and supportive care. Evidence-based vitamin D guidelines are lacking in this population.This is a retrospective study following the implementation of an institutional guideline for standardized monitoring and supplementing vitamin D based on 25-hydroxyvitamin D levels and patient age. Goal 25-hydroxyvitamin D level was defined as ≥30 ng/mL and levels were checked every 3 months.Over a period of 22 months, 69 patients (median age, 6.7 y) were included. At diagnosis, 42 patients (60.8%) were insufficient. Among insufficient patients at diagnosis, 83.3% became sufficient at first repeat level following supplementation. At completion of the study 95.6% of patients were sufficient. Insufficiency was more common in winter than summer at baseline (74.3% vs. 47.1%, P=0.03), though the impact of seasonality was overcome following the algorithm. Throughout the study 4 patients had supratherapeutic but nontoxic levels.Vitamin D replacement guidelines implemented in the pediatric and young adult acute lymphoblastic leukemia population markedly increased the percentage of vitamin D sufficient patients in a short period of time.