A Second Course of Stereotactic Image-Guided Robotic Radiosurgery for Patients with Cerebral Metastasis

The purpose of this research was to study the outcome of brain metastases in a cohort of patients undergoing a second course of stereotactic image-guided robotic radiosurgery and to identify predictors corelated with survival.

A total of 63 patients with primary malignancies underwent a second course of CyberKnife radiosurgery for intracranial progression, including recurrence and new metastases after initial stereotactic radiosurgery (SRS). Overall survival (OS) and control rate were calculated by the Kaplan-Meier method. A Cox proportional hazards model was used to analyze predictive factors for survival.

With a median follow-up duration of 12 months after second SRS, the median OS of the second course of radiosurgery was 18 months. On multivariate analysis, the sum of total planned target volume (hazard ratio, 2.112; 95% confidence interval, 1.069-4.173) and minimum dose (hazard ratio, 1.990, 95% confidence interval, 1.017-3.892) were significantly associated with OS. Median intracranial progression-free survival was 23 months. The 6-month and 12-month local control rates of the targets were 97.0% and 94.4%, respectively. Univariate analysis showed that only tumor number significantly influenced intracranial progression-free survival (P = 0.012). Nine patients (14.2%) developed brain necrosis. Median time to brain necrosis in regions in which brain necrosis occurred after a single course of SRS was not reached, compared with 16 months for those treated with repeat SRS (P = 0.041).

A second course of CyberKnife radiosurgery seems to be an effective salvage option for brain progression after initial SRS. The total planned target volume shows prediction for OS. Tumor volume of initial SRS may influence selection of the potential population that may benefit from salvage radiosurgery.