Postoperative stereotactic radiotherapy for brain metastases: results from a single-center retrospective analysis

To evaluate outcomes and prognostic factors in patients with resected brain metastases treated with postoperative SRS/SRT, and to develop a novel overall survival (OS) prognostic model. We retrospectively analyzed 70 patients (72 lesions) treated with postoperative SRS/SRT from July 2017 to May 2024. Outcomes included in-field and out-field intracranial progression-free survival (PFS), OS, and incidence of radionecrosis. Prognostic factors were identified using Cox regression. Recursive Partitioning Analysis (RPA) was used to construct an OS model. Median follow-up was 15.1 months. In-field PFS was 96.2% and 90.2%; Out-field PFS was 69.3% and 64.4% at 1 and 2 years respectively. Prior cranial radiotherapy was associated with worse out-field PFS. OS rates were 67.5% at 1 year, 46.7% at 2 years. ECOG performance status, time from surgery to radiotherapy of ≤ 56 days and biologically effective dose using α/ß of 10 (BED₁₀) ≥ 51 Gy were significant OS predictors. Radionecrosis occurred in 7 patients (10%) with median onset at 25.0 months. The novel RPA model stratified patients into 3 groups: RPA-I (ECOG < 2 & BED₁₀ ≥ 51 Gy; median OS 43.4 months, 95% CI 22.3 months-Not reached), RPA-II (ECOG < 2 & BED₁₀ < 51 Gy; median OS 11.9 months, 95% CI 3 months-19.2 months) and RPA-III (ECOG ≥ 2 regardless of BED₁₀ delivered; median OS 4.1 months, 95% CI 1.2 months - 22.0 months) (p < 0.001). RPA-II and RPA-III had higher death risk compared with RPA-I. This model outperformed existing models after bootstrapping validation. Postoperative SRS/SRT is effective for brain metastases. Appropriate patient selection, timely initiation and sufficient radiation dose improve outcomes. Our novel RPA model offers promising prognostic stratification for guiding treatment decisions.