Introduction: The aim of our study was to identify risk factors associated with distant radiographic progression in patients undergoing stereotactic radiosurgery (SRS) for brain metastases (BM).
Methods: Following IRB approval, data of 1427 patients (4283 BM lesions) who were treated using SRS at Cleveland Clinic from 2000-2012 were collected. Distant tumor progression at 3 and 6 months were the primary end points and correlated to patient related variables. Logistic regression and competing risk models were used for data analysis.
Results: The median number of targets was 2 (range 1-17) with 45% of patients having a single lesion. 45.9% of patient had lesions >2cm in size and median total intracranial tumor volume was 2.6 cc (range 0.03-83cc). Overall, 4% and 9% of patients had local progression in 3 and 6 months, respectively. Distant progression was observed in 10% and 19% at 3 and 6 months. Patients with 2-4 target lesions were more likely to develop new lesions compared to those with single lesions at 3 months (OR: 0.84, P<0.001) and 6 months (OR: 0.87, 0=0.014). Similarly, patients with 5-10 target lesions for SRS were more likely to develop new lesions at both 3 and 6 months compared to those with 2-4 lesions (OR: 0.83, CI: 0.40-0.85 and OR:0.85, CI: 0.45-0.86 respectively, p<0.05). Higher number of lesions (>5), cumulative intracranial tumor volume (CITV) (= 2.75 cc), radiographic progression after SRS, type of SRS (boost versus upfront and salvage) and tumor pathology (radio resistant) were independent predictors of distant tumor progression following SRS.
Conclusions: Number of target lesions (>5) and CITV (= 2.75 cc) are both independent predictors of distant tumor progression following SRS for BM at first and second follow up (3 and 6 months after SRS). Radio sensitivity of tumor and addition of WBRT are also predictors of distant intracranial progression.
Patient Care: The results of our study can be used in tailoring the follow up of the patients following SRS for Brain metastases (BM).
Learning Objectives: By the conclusion of this session, participants should be able to:
1) Identify various risk factors associated with distant radiographic tumor progression in patients undergoing SRS for BM.