A prospective study of linear accelerator–based stereotactic radiosurgery for brain metastases

Background/objective To prospectively evaluate the efficacy and safety of linear accelerator (LINAC)-based stereotactic radiosurgery (SRS) via a dynamic conformal arc (DCA) in brain metastases (BMs) and to investigate clinical, dosimetric, and laboratory parameters associated with treatment outcomes. Methods Sixty-six patients with 192 BMs underwent SRS using a standardized automated DCA protocol initiated in 2021. The primary endpoint was one-year control, and secondary outcomes included intracranial failure, leptomeningeal progression, overall survival (OS), and adverse effects. The significance of clinical factors, dosimetric (homogeneity index [HI] and conformity index [CI]), and laboratory markers was examined. Results The 12-month cumulative incidence of local failure was 7.7% (95% CI, 1.2%–14.2%), corresponding to 92.3% 1-year local control. Higher HI (>1.2) was significantly associated with lower local failure (12-month local failure 5.2% vs 28.6%; p = 0.04). The 12-month cumulative incidence of distant intracranial failure was 31.5% (95% CI, 20.1%–43.0%) and was higher in patients > four BMs ( p = 0.01) and total tumor volume >30 cm 3 ( p < 0.01). Leptomeningeal progression occurred in 7 patients and was marginally associated with an increased CI (>1.13, p = 0.077) and a higher neutrophil-to-lymphocyte ratio (>4.2, p = 0.089). The median OS was 11.4 months. Impaired performance status ( p < 0.01) and absence of targeted therapy ( p = 0.02) predicted lower survival independently. The treatment showed tolerability, with 3.0% of patients experiencing grade 3 radiation necrosis. Conclusion LINAC-based SRS using automated DCA demonstrated robust local control and minimal toxicity in BMs. Tumor burden, dosimetric characteristics, and systemic inflammatory markers were associated with intracranial failure patterns and survival. These findings support LINAC-based SRS as a safe and clinically effective local treatment option for BMs in contemporary oncologic practice.