Intracavitary Carrier-embedded Cs131 Brachytherapy for Recurrent Brain Metastases: a Randomized Phase II Study

Inclusion Criteria: * Adult patients ≥ 18 years of age who are capable of giving consent * Undergoing elective craniotomy for resection of a previously-irradiated brain metastasis with suspicion for viable disease at the time of consent, and anticipated achievement of gross-total or near-total (\>/=95%) resection * Karnofsky Performance Status score (KPS) of ≥70 * Ability to undergo brain MRI with gadolinium Exclusion Criteria: * Unable to tolerate MRI or CT imaging * Pregnancy (patients must have a negative pregnancy test within 30 days of the operation) * Women must agree to not breastfeed for at least 12 weeks after the procedure (lactating and discarding in that interval allowable) * Diagnosis of leptomeningeal carcinomatosis or \>5 additional active or untreated CNS lesions for a total of \>6 active lesions * Prior irradiation (EQD2) in excess of 100 Gy to site of implant, using an α/β of 2 * Apposition of tumor margin to brainstem or optic apparatus * Previous infection within the operative field, current active systemic infection requiring systemic therapy, or immunodeficiency * Urgent surgery required prior to availability of brachytherapy Intraoperative Exclusion Criterion: * Patients will be excluded if intraoperative pathology is not consistent with \>/=5% viable metastatic disease.