MMAP-12 CONVENTIONAL SURGICAL RESECTION VERSUS STEREOTACTIC RADIOSURGERY FOR 1-3 CM SINGLE BRAIN METASTASES

Abstract There is a paucity of studies comparing conventional surgical resection (CSR) and stereotactic radiosurgery (SRS) for single brain metastases (BMs). This study evaluates local treatment failure (LTF) in patients with single, treatment-naïve BMs measuring 1–3 cm in diameter, eligible for either SRS or CSR. We identified patients treated between 1998–2024 with either upfront single-fraction SRS or CSR with adjuvant or neoadjuvant radiation. Fine and Gray’s method was used to analyze predictors of LTF, and propensity score-matched analysis (PSMA) ensured cohort comparability between SRS and CSR by primary tumor type, systemic disease extent, and tumor volume. Among 645 patients (523 SRS; 122 CSR + radiation), CSR was associated with significantly lower 1- and 2-year cumulative LTF rates (4% and 8%) compared to SRS (19% and 23%; p=0.0001). Median tumor volume pre-matching was 7.45 cm³ for CSR and 1.80 cm³ for SRS (p<0.0001). On multivariate analysis, predictors of increased LTF included SRS (HR=5.1, 95% CI: 2.6–9.8; p<0.0001), melanoma (vs renal cell carcinoma, HR=2.2, 95% CI: 1.2-4.3; p=0.018), colorectal cancer (vs RCC, HR=3.4, 95% CI: 1.4-7.8; p=0.005), breast cancer (vs RCC, HR=2.4, 95% CI: 1.1-5.2; p=0.037), greater tumor volume (HR= 1.2, 95% CI: 1.0-1.4 per fold increase; p=0.032), and eloquent location (vs non-eloquent, HR=1.8, 95% CI: 1.1-2.8; p=0.014). In 84 matched pairs, CSR remained associated with lower 1- and 2-year LTF rates (5% and 9%) vs SRS (28% and 37%; HR=0.2; p<0.0001). Among patients with tumor volume ≤5.71 cm³ (2.2 cm diameter; n=69), SRS was significantly associated with local recurrence (HR= 13.5, 95% CI: 3.2-56.2; p=0.0004). In conclusion, for single BMs measuring 1–3 cm, CSR was associated with significantly lower LTF compared to SRS, particularly for lesions <2.2 cm or those from melanoma, breast, or colorectal primaries. These findings support the consideration of CSR to optimize local control.