Impact of stereotactic radiosurgery dose on local control and radiation necrosis in metastatic brain lesions: a comparative study.

PURPOSE: This study aimed to evaluate and compare the efficacy of stereotactic radiosurgery (SRS) prescription doses on local control (LC) rates of brain metastases and radiation necrosis (RN) risk. METHODS: A retrospective review was conducted on patients treated between January 2018 and December 2023 at a single institution with single-fraction SRS at doses of 20 Gy, 22 Gy, or 24 Gy. The effects of radiation dose on LC and RN were evaluated using univariate analysis, then with multivariate logistic regression adjusting for gross tumor volume (GTV) and history of post-SRS whole-brain radiation therapy (WBRT). RESULTS: The study included 332 brain metastases from 159 patients. 127 lesions were treated with 20 Gy (38.3%), 183 with 22 Gy (55.1%), and 22 with 24 Gy (6.6%). Median follow-up was 14 months. One-year LC rates were 96.3% for 22 Gy versus 90.1% for 20 Gy (p = 0.032). On multivariable logistic regression, 22 Gy was still associated with higher odds of 1-year LC compared with 20 Gy (adjusted OR 3.04, 95% CI 1.22-7.59; p = 0.017). Both SRS dose and GTV were independent predictors of RN (dose adjusted OR 2.05, p = 0.016; GTV adjusted OR 1.40 per doubling volume, p < 0.001). Overall survival did not differ significantly by dose (p = 0.63). CONCLUSION: In this retrospective cohort, SRS at 22 Gy was associated with higher local control than 20 Gy. Larger GTV volumes were independently associated with a higher risk of RN. WBRT post SRS was not an independent risk factor for RN.