# Stereotactic Radiosurgery for Patients With Five or More Brain Metastases: Retrospective Single-Institution Analysis of Prognostic Factors

## TL;DR

This study examines outcomes and factors affecting survival in patients with five or more brain metastases treated with radiosurgery, identifying key predictors of prognosis.

## Contribution

The study identifies BMV as a more prognostic factor than vBMV for survival in patients with multiple brain metastases treated with SRS.

## Key findings

- Patients with progressive extracranial disease and lower GPA scores had significantly worse survival outcomes.
- BMV was more strongly associated with overall survival than vBMV in multivariable analyses.
- Forty-two patients developed new brain metastases after SRS, while 28 did not.

## Abstract

Purpose: We describe patient outcomes and prognostic factors following linear accelerator-based stereotactic radiosurgery (SRS) for five or more brain metastases, without prior or planned whole-brain radiotherapy.

Methods: We identified 116 eligible patients treated with SRS from 2019 to 2024 for newly diagnosed brain metastases. We describe clinical factors associated with survival ≤2 months and analyze brain metastasis velocity measured as the number (BMV) or volume (vBMV) of new metastases per year.

Results: The number of treated brain metastases ranged from 5 to 41 (median 10); net lesion volume ranged from 0.1 to 59.8 (median 5.2) cc. Primary cancers included non-small cell lung (n=65), melanoma (n=20), breast (n=19), kidney (n=6), gastrointestinal (n=4), and other (n=4) cancers. The 6-, 12-, and 24-month overall survival (OS) was 60.3%, 40.5%, and 28.0%, respectively. A progressive extracranial disease at the time of brain metastases and lower predicted survival from graded prognostic assessments (GPAs) were significantly adverse factors for OS on multivariable Cox regression and were associated with ‘poor survivors’ who died ≤2 months from SRS (n=21) or at >2 months but opting against post-SRS cancer care and follow-up imaging (n=6; OS=2.1-5.8 months). Forty-two patients developed new brain metastases after SRS, while 28 (after ≥6-month follow-up) did not. Among these patients, OS was significantly associated with BMV and vBMV, though vBMV was not significant on multivariable Cox regressions that included BMV.

Conclusions: For patients with five or more brain metastases, clinical factors, including the status of extracranial disease and GPA, can potentially aid in selecting patients best-suited for SRS for multiple brain metastases, versus potentially deferring SRS in favor of supportive care. While vBMV is associated with OS, BMV appears more prognostic.