Effectiveness of Standard Margin Stereotactic Radiosurgery Dose to Brain Metastases

This study aims to assess efficacy of a 15-Gy margin dose in terms with the hypothesis that efficacy will be comparable with historical controls with fewer radiation-related side effects.

Patients who received single-fraction stereotactic radiosurgery (SRS) for metastatic brain tumors (prescribed 1500 cGy with 2-mm planning tumor volume) at the University of Missouri Hospital between 2004 and 2018 with at least 3 months of follow-up were retrospectively reviewed. Demographics, lesion dimensions, concurrent therapy, and treatment history before SRS were assessed. Outcomes included local control, distant control, radiation-related changes, survival, repeat SRS or whole-brain radiation therapy, and side effects. Data from the literature were pooled for a meta-analysis.

A total of 142 patients had at least 3 months of follow-up data available. The 12-month actual local control rate among these patients was 92% per tumor. The overall intracranial control rate was 66.9% per patient. Radiation-related side effects occurred in 32.4% of patients (n = 46), with some patients having more than 1 side effect. Radiation-related radiographic changes occurred in 48 lesions (10.6%) in 37 patients (26%). Pathologically confirmed radiation necrosis occurred in 19 lesions (4%) and in 18 patients (12.6%). Local and distant control rates for this population was comparable with historical controls. Side effects in the literature are inconsistently reported, so rigorous comparative analysis is not possible.

A single-fraction radiosurgery margin dose of 15 Gy to the planning tumor volume can effectively provide local control and distant control and is comparable with historical controls, which use 18-25 Gy, with a good toxicity profile.