CNSC-80. EVALUATION OF TOCILIZUMAB IN CHILDHOOD ADAMANTINOMATOUS CRANIOPHARYNGIOMA: AN INTERNATIONAL CASE SERIES

Abstract BACKGROUND Childhood adamantinomatous craniopharyngiomas (ACP) are low-grade brain tumors associated with significant morbidity and treatment-related complications. Tocilizumab (TCZ), a monoclonal antibody targeting the IL-6 receptor, may mitigate tumor-associated inflammation, as IL-6 is elevated in both cystic and solid components of ACPs. Preliminary data suggests that TCZ may reduce or stabilize cystic volume within 3–6 months. This two-center retrospective series evaluated the impact of TCZ on tumor volume and clinical outcomes. METHODS Children with ACP received TCZ (10-12 mg/kg every 2-4 weeks) at different disease stages at UCSF (n=9) and the Princess Máxima Center (n=5). Tumor response was assessed by MRI at baseline and approximately every 3 months during treatment. Clinical effects were monitored through evaluations of vision, hypothalamic-pituitary function and adverse events. RESULTS Fourteen children (median age 7.5 years (1–16y), 57% female) received TCZ with a median duration of 10.6 months (6months - 4 years). Thirteen had undergone surgery and/or cyst fenestration and five received radiation therapy prior TCZ initiation. A reduction in the cystic component was observed in 9 patients (64%), with 5 demonstrating stable solid components. Among these, 2 underwent cyst drainage during TCZ treatment, and 1 additionally received bevacizumab. The median time to best response was 6 months (3–12m). Cystic progression occurred in 5 patients (36%), 3 of these exhibited growth in the solid component after a median time of six months. One patient initially received tocilizumab monotherapy; bevacizumab was added after 1.5-3 years in response to cystic growth, resulting in sustained cyst stabilization. All patients had regular ophthalmologic evaluations. Two showed mild visual field improvement. Hypothalamic-pituitary function remained stable. CONCLUSION Tocilizumab was well tolerated and associated with cystic volume reduction in a subset of patients. The addition of bevacizumab led to ongoing responses after single agent TCZ failed. Volumetric MRI assessment is ongoing.