Recurrent C19MC-altered embryonal tumors with multilayered rosettes: outcomes of stereotactic radiosurgery

Embryonal tumors with multilayered rosettes (ETMR) are aggressive grade IV brain tumors primarily affecting children under age 3. Despite intensive multimodal therapy, prognosis remains poor, and salvage protocols for localized recurrence are not standardized. Traditional radiotherapy is frequently deferred in young children to protect neurocognitive function. Herein, we evaluate the efficacy of stereotactic radiosurgery (SRS) as focal treatment for recurrent ETMR.

We retrospectively reviewed three pediatric patients with molecularly confirmed C19MC-altered ETMR, treated with mask-based SRS for localized recurrence. Data regarding molecular profiles, prior treatments, SRS dosimetry, and longitudinal clinical outcomes were analyzed.

All patients underwent initial gross total resection and adjuvant chemoradiotherapy before experiencing localized recurrence. In case 1, a 3-year-old female received multiple SRS courses for serial recurrences and remains stable 22 months post-diagnosis. Case 2, a 4-year-old female, achieved local control at the primary recurrence site following SRS but developed diffuse spinal leptomeningeal spread 10 months later and succumbed to the disease 20.5 months post-diagnosis. In case 3, a 3-year-old female received SRS for a nodular recurrence and remains disease-free 16 years after initial diagnosis. Across all cases, SRS was well-tolerated without acute neurotoxicity.

SRS demonstrates promise as a salvage strategy for localized ETMR recurrence. It may extend survival and, in select cases, facilitate long-term local control while minimizing neurocognitive burden typically associated with large-field re-irradiation. Notably, the efficacy of SRS cannot be separated from concurrent salvage therapies in this highly multimodal treatment context. Further investigation is needed to define the role of SRS within multimodal protocols for ETMR.