Objectives: The aim of the study was to asses efficacy and safety of robotic stereotactic radiosurgery (SRS) in the treatment of brain metastases in patients who were previously treated with the use of SRS. Methods: A retrospective analysis of clinical data of a group of 38 patients who underwent SRS at least twice. All patients were in good performance status (mean and
median Karnofsky Performance Status - 80). Mean age was 57 years (range 34 - 79 years), 66% of patients were female. In 32% of patients location of primary tumor was lung, in 29% - breast, in 13% - kidney. Median time between the diagnosis of the primary tumor and brain metastases was 26 months, mean - 43 months (range 0 - 185 months). In 13% of patients brain metastases were found prior to diagnosis of the primary tumor. Planned dose was delivered in 1 - 3 fractions, 55% of patients were treated with single fraction. Mean total tumor volume of brain lesions was 8.86 mL, median - 4.62 mL (range 0.06 - 52.2 mL). Radiological evaluation of the treatment effects was performed in 82% of patients. For statistical analysis Kaplan - Meier estimator and log-rank test were used. Results: Median overall survival (OS) in the whole group was 21 months. Longer OS was observed in patients with single brain metastasis as compared to those with multiple lesions (p = 0.001). Median OS calculated from the second treatment - nearly 11 months. Acute toxicity (including headache, dizziness, and fatigue) was observed in 10% of patients. Additional whole brain radiotherapy was not associated with longer OS, neither was systemic treatment. Significantly shorter OS was observed in patients with progressive systemic disease (p = 0.037). Higher total tumor volume (>7 mL) was associated with shorter OS (p = 0.019). Median progression free survival was 17.5 months. In multivariate analysis statistically significant predictors of OS were multiple brain metastases (p = 0.0037) and total tumor volume (p = 0.018). Conclusions: Repeated stereotactic radiotherapy in patients with brain metastases is a well-tolerated and effective treatment. In patients suitable for repeated treatment the extent of brain invasion is the main adverse prognostic factor.