Introduction: Adverse radiation effect (ARE) after stereotactic radiosurgery (SRS) for brain metastasis (BM) patients is a dreaded complication that often leads to significant compromise in the patient’s quality of life. Here, we sought to determine risk factors associated with ARE following SRS.
Methods: We identified 214 BM patients (1,106 BM) treated between 2007 and 2017 at our institution with >3 months of MRI follow up. We collected pertinent demographic, clinical, and SRS parameters. ARE was defined as the presence of FLAIR hyperintensity in >25% of the area of any of four axial MRI images defined by 1) the centrum semiovale, 2) third ventricle, 3) temporal horns, and 4) the fourth ventricle. Statistical analysis was carried out using Student’s t-test, Pearson’s chi-squared test, and univariate and multivariate logistic regression.
Results: Of the 214 patients, 62 patients (28.97%) suffered ARE following SRS. On univariate logistic regression, the odds of ARE were increased with higher cumulative intracranial tumor volume (CITV) (odds ratio (OR) 1.026 per 1 cm3 increase, 95% CI 1.009 - 1.043, p= 0.003), >4 rounds of SRS sessions (OR 9.545, 95% CI 1.924 - 47.352, p=0.006), and prior history of whole-brain radiation therapy (WBRT) (OR 4.459, 95% CI 2.233 - 8.907, p<0.001). On multivariate logistic regression adjusted for length of follow-up, these associations remain robust: CITV (p=0.036), >4 rounds of SRS (p=0.033), and prior history of WBRT (p<0.001). Variance analysis indicated that the relative importance of these risk factors in contributing to ARE, in descending order, is: prior history of WBRT, CITV, and >4 rounds of SRS.
Conclusions: In this analysis of our decade-long experience, we discovered three risk factors for ARE, including prior history of WBRT, increasing CITV, and >4 rounds of SRS. Consideration of these factors should facilitate patient counseling and clinical decision making.
Patient Care: A deeper understanding of the risk factors contributing to adverse radiation effect will facilitate patient counseling and clinical decision making.
Learning Objectives: 1. Identify risk factor for adverse radiation effect in patients with brain metastases treated with stereotactic radiosurgery
2. Describe the relative importance of each of these factors in contributing to this complication