Outcomes in long-term survivors treated with stereotactic cranial radiotherapy for brain metastases

This study aimed to characterize long-term intracranial control, recurrence patterns, radiation necrosis (RN) risk, and treatment intensity among patients with ≥ 24 months of follow-up after stereotactic cranial radiotherapy (SRT).

We conducted a retrospective review of patients treated with SRT at a single institution from 2018 to 2023. Eligible patients received at least one course of SRT and had ≥ 104 weeks of follow-up. Clinical, treatment, and radiologic data were collected as well as in-field and out-of-field failure, RN incidence and management, survival, and treatment patterns over time.

Fifty-one patients met the inclusion criteria, contributing 130 SRT courses treating 241 lesions. Median follow-up was 33.8 months. Most patients (51%) had non-small cell lung cancer, and 80% received systemic therapy after initial SRT. In-field failure occurred in 16.2% of lesions and 47.1% of patients, with higher failure rates in resection cavities than in intact metastases. Out-of-field failure occurred in 47.1% of patients, most commonly managed with additional SRT. The 2‑year in-field and out-of-field recurrence-free rates were 47.7% and 56.6%, respectively. Radiation necrosis developed in 21 lesions (8.7%), with substantially higher incidence in resection cavities (29.4%) and re-irradiated targets. Median time to RN was 11.2 months, and 38% required surgical intervention. Five-year overall survival was 67.8%.

Among long-term survivors treated with SRT, both intracranial recurrence and RN remain clinically significant. As patient survival improves, individualized surveillance, careful consideration of cumulative radiation exposure, and optimized re-irradiation strategies are essential to minimize toxicity while maintaining durable intracranial control.