Stereotactic Radiosurgery In the Management of Extensive Brain Metastases In Patients with over 25 Lesions
Abstract
Purpose
To explore critical unanswered questions in the radiosurgical management of patients with ≥25 cumulative brain metastases (BMs), specifically: (1) whether dose-volume thresholds to uninvolved brain exist beyond which neurotoxicity becomes unacceptable, (2) whether single-session stereotactic radiosurgery (SRS) can safely replace whole-brain radiotherapy (WBRT) as initial therapy for this population, and (3) whether hippocampal dose constraints used for hippocampal-avoidance WBRT are maintained with single-session SRS.
Methods
In this multicenter retrospective cohort study, patients with ≥25 cumulative BMs treated with single-session SRS and ≥6 months follow-up were analyzed. Dosimetric variables included whole-brain dose volumes (V12, D100, median dose), brainstem and optic apparatus maximum doses, and hippocampal dose metrics. Early outcomes included feasibility of delivering SRS with acceptable critical structure doses. Planned analyses in the full cohort of 40 patients include examination of dose-volume relationships to uninvolved brain and associations with neurotoxicity, comparison of survival and functional outcomes between patients treated with SRS versus those treated with WBRT, and assessment of hippocampal dose exposure relative to published hippocampal-sparing thresholds.
Results
Preliminary analysis of 10 patients shows that single-session SRS for extensive BMs can be delivered with relatively low whole-brain median doses and limited high-dose exposure to hippocampi and other critical structures. No early outliers suggest overtly excessive dose to uninvolved brain or hippocampus. Dosimetric profiles support continued investigation of threshold effects and potential equivalence to WBRT in selected patients.
Conclusion
These initial data support the technical feasibility of single-session SRS in patients with ≥25 brain metastases and provide compelling rationale to investigate dose-volume thresholds for neurotoxicity, compare SRS versus WBRT outcomes, and evaluate hippocampal dose safety. Results from the complete cohort will inform optimal radiosurgical strategies for extensive intracranial metastatic disease.