Placement of cesium-131 permanent brachytherapy seeds in periventricular high-grade gliomas: case report highlighting a novel technique to prevent seed migration. Illustrative cases

BACKGROUND Reirradiation of recurrent high-grade gliomas (HGGs) with external beam radiation therapy is limited by the risk of radiation necrosis (RN). Intraoperative brachytherapy offers a localized radiation approach that minimizes RN risk while maintaining tumor control. However, seed migration has historically limited its use in periventricular regions. The authors present 3 cases of recurrent periventricular HGG (2 IDH-wildtype, MGMT promoter–methylated, EGFR-amplified WHO grade 4 glioblastoma and 1 WHO grade 3 astrocytoma) in which a three-layered barrier was created between the ventricular lining and tumor cavity to prevent seed migration, enabling successful brachytherapy. OBSERVATIONS Following maximal safe resection, a three-layered patch separated the resection cavity from the ventricle prior to cesium-131 (¹³¹Cs) brachytherapy. Patient 1 received suture-stranded¹³¹Cs (20 seeds), while patients 2 and 3 received¹³¹Cs GammaTile (6 tiles, 4 seeds per tile). A three-layered barrier was formed using Gelfoam, Surgicel, and Adherus. At a median 22-month (range 11–24 months) follow-up, MRI confirmed no seed migration and seeds remained in the cavity. There were no complications associated with the barrier placement. LESSONS This study highlights the novel use of this technique in preventing¹³¹Cs seed migration in intraoperative brachytherapy, serving as a proof-of-concept study.