KEY POINTS
- The focused narrative review retained 18 core studies, including 13 clinical/workflow reports and five planning or dosimetry studies, and uses postoperative cavity treatment for brain metastases as the main contemporary model.
- Modern intracranial brachytherapy is predominantly permanent low-dose-rate treatment using Cs-131 or I-125. Cs-131 has a substantially shorter half-life—approximately 9.7 days versus 59.4 days for I-125—allowing more dose to be deposited early after surgery.
- Contemporary GammaTile uses four Cs-131 seeds in a 2 × 2 cm collagen carrier, with approximately 10-mm inter-seed spacing and 3-mm source-to-tissue offset. A typical reported prescription is approximately 60 Gy at 5-mm depth.
- Alternative stranded Cs-131 implantation allows more customization for irregular cavities, commonly using 5-mm intra-strand spacing and 7–10-mm separation between seed lines, but places greater dependence on intraoperative operator geometry.
- Planning is explicitly iterative: preoperative MRI estimates cavity geometry and source requirements, the implant is adapted to the actual surgical cavity, and postimplant CT within roughly 12–72 hours is used for source reconstruction and dosimetric verification.
- Published selected brain-metastasis series report approximately 79–100% 1-year local control for newly diagnosed lesions and 83–100% for recurrent lesions. One matched comparison reported local recurrence of 10.0% after resection + Cs-131 versus 28.3% after resection + postoperative SRS, but the review stresses major cross-study heterogeneity.
- The paper emphasizes that safe implementation requires more than treatment planning: source ordering/accounting, sterile handling, intraoperative coordination, radiation safety, postimplant imaging and independent QA all need predefined workflows. Prescription definitions and outcome-linked dosimetric thresholds remain incompletely standardized.
CLINICAL TAKEAWAY
Modern brain brachytherapy should be viewed as a multidisciplinary procedural program rather than simply another radiation plan. Cs-131 platforms offer immediate cavity-directed treatment and avoid postoperative cavity remodeling, but SRS remains supported by a broader mature evidence base and standardized outcome-linked brachytherapy constraints are still lacking.