Intraoperative Cs-131 Brachytherapy for Recurrent Brain Neoplasms: Initial Experience and Dosimetric Outcomes
Abstract
Purpose
Re-irradiation of brain neoplasms remains a significant clinical challenge. Resection without adjuvant re-irradiation is associated with a high local failure rate, whereas re-irradiation alone may improve local control but is associated with a high risk of radiation necrosis. Salvage resection combined with cesium-131 (Cs-131) brachytherapy may offer dosimetric and biologic advantages. The purpose of this study is to present our initial experience with Cs-131 cranial brachytherapy and to characterize post-operative dosimetry in patients with recurrent brain neoplasms.
Methods
Patients with recurrent glioblastoma (GBM), brain metastases or meningioma underwent surgical resection of the tumor, followed by intraoperative implantation of Cs-131 tiles. Preoperative estimation of the number of tiles required was performed using MiM Symphony software or a vendor-provided planning tool. Post-implant dosimetric analysis was performed using MiM software and post-operative CT and MRI. A prescription dose of 60 Gy was delivered to a depth of 5 mm from the resection cavity surface. Dosimetric parameters for the clinical target volume (CTV) and the brain tissue were collected.
Results
Twenty patients were treated between October 2023 and January 2026, including 11 GBM, 6 brain mets, and 3 meningioma. Mean tumor volume was 26.5±19.3 cm3 (range: 7.1-78.7 cm3. The average number of implanted tiles was 6.1±1.9. Mean CTV D90% was 58.7±15.4 Gy, and mean CTV V100% was 82.8±14.9%. The V10Gy to the brain ranged between 126.5 and 384.6 cc with a mean of 232.2±98.2 cc.
Conclusion
Cs-131 brachytherapy following salvage resection is a feasible re-irradiation strategy for recurrent brain neoplasms. Characterization of implant dosimetry is an essential step toward optimizing this intraoperative technique and informing dose distribution to surrounding brain tissue. Ongoing analysis will evaluate clinical outcomes and treatment-related toxicity.