Cesium-131 tile brachytherapy (TBRT) slashes surgical-bed recurrence vs post-op SRT in resected brain mets

ROADS (NCT04365374) was an open-label, randomized Phase 3 trial across 32 US centers comparing resection + post-operative stereotactic radiation therapy (SRT; standard approach for cavity control) vs resection + intraoperative cesium-131 tile-based radiation therapy (TBRT; collagen tiles embedded with Cs-131 seeds placed at surgery) for a single newly diagnosed resectable brain metastasis (up to 5 additional unresected lesions allowed; treated with SRT in both arms); the mITT population was 204 patients (101 SRT, 103 TBRT) with median follow-up 12.9 months. Surgical bed recurrence was 11.9% with SRT vs 1.0% with TBRT; median time to surgical bed recurrence was 17.4 months vs not reached (HR 0.06, p=0.007) and surgical bed recurrence–free survival improved (median 10.9 months vs not reached; HR 0.48, p=0.002)—notably below typical post-op cavity SRS/SRT local failure rates in contemporary series (often ~5–15% at 1 year, depending on cavity size/timing). OS also favored TBRT (HR 0.59, p=0.032; estimated 24-month OS 61.7% vs 35.7%), while safety looked similar (grade ≥3 TRAEs 18.1% vs 19.3%; radiation necrosis 7.8% vs 6.9%); total cranial treatment completion was dramatically faster with TBRT (median 1 day vs 30 days), though leptomeningeal disease numerically trended higher with TBRT (9.7% vs 3.0%; p=0.146).