# Volumetric Modulated Arc Therapy for Radiosurgery of Brain Metastases: A Single-Center Study
## 1 Introduction  
Currently, brain metastases (BMs) represent the most frequent intracranial tumor, occurring in about 20-40% of cancer patients [1; 2]. Improved diagnostic imaging techniques (e.g., magnetic resonance imaging), as well as more effective treatment regimens, have contributed to the increased incidence of BMs, making the therapeutic approach to BMs anemerging challenge [3; 4; 5; 6]. The clinical management of patients with BMs currently includes both systemic treatment (chemotherapy and/or targeted therapies, among others) and local treatment (neurosurgical and/or radiotherapeutic treatment). Whole-brain radiotherapy (WBRT) and stereotactic radiosurgery (SRS) are two treatment modalities commonly used to treat BMs. Traditionally, radiotherapeutic treatment has been carried out by WBRT. This involves the administration of a radiation dose to the entire brain parenchyma (although hippocampal-sparing WBRT is more dose-selective for different areas of the brain), usually in multiple treatment sessions. However, recent evidence has revealed the potential development of cognitive impairment [7; 8]. In this context, SRS has become increasingly relevant. The radiosurgery technique involves the administration of a highly concentrated dose of radiation to the lesion with an extremely strong dose gradient in the surrounding area in order to minimize side effects on healthy brain tissue [9].  
Volumetric modulated arc therapy (VMAT) is a radiotherapy technique that has been rapidly implemented in most cancer treatment settings due to its high efficiency compared to other intensity modulated radiotherapy (IMRT) techniques [10]. One of the strengths of VMAT radiosurgery compared to other radiosurgery techniques (such as gamma-knife radiosurgery) is that it does not require a stereotactic frame (frameless technique), which, together with its shorter procedure time, has facilitated its integration into radiation oncology departments [11]. In this context, neuro-oncological variables that may have a significant impact on patient survival should also be assessed. To date, some factors that have been shown to influence the survival of patients with BMs are the type and histology of the primary cancer, treatment of the primary cancer, and clinical characteristics such as age, size/number of BMs, Karnofsky performance score, and the effect of extracranial disease [12; 13]. Another emerging factor to take into consideration that could have an impact on both survival and some clinical aspects of patients with BMs would be tumor-related epilepsy. Epilepsy related to tumor lesions is present in 20-35% of patients with BMs. Among the main risk factors described are metastases of melanoma and pulmonary origin, those with hemorrhagic components, and cortico-subcortical localization [14; 15].  
This work aims to answer some questions of interest in relation mainly to the clinical characteristics of patients treated with SRS as well as the variables with potential impact on patient survival. So, the objectives of the present study are to analyze: (a) the main clinical-demographic characteristics of a cohort of patients with BMs treated with VMAT-RS including the prevalence of epilepsy in different primary tumor types; (b) overall survival (OS) after radiosurgery treatment and the potential prognostic factors for survival; and (c) local control after treatment.