TRLS-07. Intracavitary carrier-embedded Cs131 brachytherapy for recurrent brain metastases: A randomized phase II study

Background The salvage treatment of recurrent brain metastases after failed irradiation is a clinical challenge. Adjuvant SRS is standard of care for resected brain metastases in the upfront post-resection setting given a significant local control advantage over surgery alone. However, the role of reirradiation following salvage resection of recurrent post-irradiation metastases is unclear owing to both reduced efficacy of subsequent courses of external beam radiation, and likely increased risk of radiation injury. Intracavitary cesium 131 (Cs131) brachytherapy offers a highly conformal adjunct radiation option that we hypothesize may allow for improved local control while also theoretically conveying a low risk of radiation necrosis. In this randomized controlled study, we aim to define the potential benefits and risks of resection plus permanently implanted, carrier-embedded intracavitary Cs131 brachytherapy versus conventional care (surgery alone). Methods This is a single-center randomized controlled study of patients undergoing resection of recurrent, previously-irradiated brain metastases. Exclusion criteria include prior in-field infection, prior radiation >100Gy (in 2Gy fraction equivalents), >5 additional active or untreated CNS lesions, or leptomeningeal carcinomatosis. Subjects are randomized 1:1 to undergo either surgery with placement of Cs131 brachytherapy or surgery alone. The primary endpoint is freedom from treated-site progression at 9 months. Secondary endpoints include wound complications at 3 months and time to local retreatment at the index site, and exploratory objectives include neurocognitive function prior to surgery and at 3 and 12 months postoperatively, with correlative analyses of the previously irradiated brain metastasis tissue. Accrual began on December 24, 2020 and 5 of a planned 76 patients have enrolled. This is the first randomized controlled trial of surgery plus permanently implanted intracavitary Cs131 brachytherapy versus surgery alone for recurrent brain metastases. ClinicalTrials.gov Identifier: NCT04690348