Stereotactic radiosurgery practice patterns for brain metastases: a survey by the SRS_SBRT_SEOR (Spanish Society of Radiation Oncology) Working Group

Abstract

Background: This study evaluates practices and preferences in treating intact brain metastases with stereotactic-radiosurgery (SRS) among members of the SEOR-SRS_SBRT working group, focusing on clinical protocols, equipment usage, and treatment parameters.

Materials and methods: A survey conducted via Google Forms targeted 149 group members, with responses collected from one representative per institution between April and May 2024. Respondents included radiation oncologists from Mexico, Argentina, Portugal, and Spain, and data analysis covered demographics, equipment, treatment protocols, immobilization techniques, dose schedules, image-guided radiation therapy (IGRT), and prescription criteria.

Results: Out of 149 members, 28 institutions responded. Most participants (64.5%) had over 10 years of experience. Single-fraction-SRS was practiced by 64.5%, while fractionated SRS-SRT was used by 96.8%. Linear accelerators (C-Linac) were the primary equipment (86.7%). Specific protocols for brain metastases were reported by 80%. SRS was preferred for 1-3 metastases (93.3%), while whole-brain radiation therapy (WBRT) was used for > 10 metastases (70%). Considering the type of stereotactic localization, frameless systems were employed in 69% while rigid-frames were used in 31% of cases. The most common immobilization technique was a reinforced mask (50%). Planning computed tomography (CT)/magnetic resonance imaging (MRI) slice thickness ≤ 2 mm was standard, and automatic registration was applied in 69%. Doses of 21-23 Gy were common for lesions < 1 cm, while < 20 Gy was typical for 2-3 cm lesions. Margins for single-fraction SRS were 1 mm in 50% of cases. IGRT verification used cone-beam CT (64.5%) and surface-guided radiation therapy (35.5%).

Conclusion: The findings reveal variability in SRS practice, particularly in immobilization, dose prescriptions, and IGRT methods, emphasizing the need for standardized guidelines to optimize patient outcomes and adapt treatments to institutional resources and patient-specific factors.

Keywords: CNS; local control; multiple brain metastases; radiosurgery.