CyberKnife Robotic Radiosurgery System for Treating Large Brain Metastases: A Single-Center Cohort Study

This study evaluated local control and overall survival following hypofractionated stereotactic radiosurgery (HF-SRS) using the CyberKnife system for brain metastases ≥ 10 cm³, addressing the challenges of balancing efficacy and toxicity in larger lesions.

We enrolled patients with 1-4 newly diagnosed brain metastases from lung or breast cancer. The primary endpoint was local control of the treated metastases. The secondary endpoints were overall survival and incidence of radiation necrosis. Survival endpoints were evaluated using the Kaplan-Meier method. A Cox proportional hazards regression model was used to test for significant associations between clinical factors and outcomes.

Between December 2016 and December 2018, 63 patients with 65 large brain metastases were included in this study. Of all the 63 cases, 55 cases were initially treated with HF-SRS; eight had tumour recurrence after gamma knife treatment. The radiosurgical margin dose (median, 30 Gy; range, 25-34 Gy) was prescribed at an isodose curve of 60%-75% (median, 67%) with multiple fractions (median, three fractions; range, 2-4), targeting a median tumour volume of 18.1 cm³ (range, 10.1-39.6 cm³). The median follow-up was 19 months. The local tumour control rates were 100%, 100%, and 92.58% at 6, 12, and 18 months, respectively. The 6-, 12-, and 18-month survival rates were 95.24%, 82.51%, and 68.61%, respectively. The cumulative incidence of radiation necrosis in patients who underwent primary HF-SRS was 7.02% and 14.04% at 1 year and 18 months, respectively.

We report our experience treating large brain metastases with HF-SRS. HF-SRS showed favourable local control with low incidence of complications.