# Volumetric Modulated Arc Therapy for Radiosurgery of Brain Metastases: A Single-Center Study
## 3 Results
### Brain Metastases  
A total of 229 BMs treated with VMAT-RS were collected from the entire cohort of 121 patients. Of the total BMs treated, 206 were treated as a single fraction (SRS), while 23 were treated fractionally (fSRS). The median dose prescribed for those patients treated with SRS was 18 Gy (range 12-20 Gy), while for those treated with fSRS it was 30 Gy (range 30-35 Gy) administered in 5-6 treatment fractions. The median accumulated tumor volume of the treated BMs was 3.25 cc (IQR 6.13).  
Regarding the distribution of BMs in the CNS, the prevalence by topographic regions was as follows (from most to least frequent): (a) frontal lobe (\(n\) = 80; 34.9%), (b) parietal lobe (\(n\) = 45; 19.7%), (c) cerebellum (\(n\) = 33; 14.4%), (d) temporal lobe (\(n\) = 25; 10.9%), (e) occipital lobe (\(n\) = 23; 10%), (f) basal ganglia (\(n\) = 5; 2.2%), and (g) remainder (\(n\) = 18; 7.9%) (Figure 3). The latter group is made up of: brain stem (\(n\) = 4; 1.7%), insula (\(n\) = 3; 1.3%), sulcus of Rolando (\(n\) = 2; 0.9%), extra-axial (\(n\) = 2; 0.9%), thalamus (\(n\) = 1; 0.4%), subthalamic nucleus (\(n\) = 1; 0.4%), amygdala (\(n\) = 1; 0.4%), choroid (\(n\) = 1; 0.4%), hypophysis (\(n\) = 1; 0.4%), ventricular atrium (\(n\) = 1; 0.4%), and fornix (\(n\) = 1; 0.4%).  
\begin{table}
\begin{tabular}{c c c c} \hline \hline  & None & 88 & (72.7) \\ Previous treatment, \(n\) (\%) & Surgery & 3 & (2.5) \\  & WBRT & 27 & (22.3) \\  & Prophylactic WBRT & 3 & (2.5) \\ \hline  & None & 84 & (69.4) \\  & WBRT & 15 & (12.4) \\ Posterior treatment, \(n\) (\%) & Single or fractionated SRS & 14 & (11.6) \\  & SRS + WBRT & 7 & (5.8) \\  & Surgery & 1 & (0.8) \\ \hline PFBMs patients, \(n\) (\%) & Patients with 1 or more PFBMs & 29 & (24) \\ \cline{2-4}  & Patients without PFBMs & 92 & (76) \\ \hline BMs treated with SRS & Median (IQR) & 1.0 & (1.0) \\ (First treatment) & Mean (SD) & 1.7 & (0.96) \\ \hline Prescription dose BMs, Gy & SRS, median (IQR) & 18 & (0.8) \\  & fSRS, median (IQR) & 30 & (0.5) \\ \hline Gross tumor volume, cc & SRS, median (IQR) & 0.8 & (2) \\ (GTV) & fSRS, median (IQR) & 4.1 & (10) \\ \hline Planning target volume, cc & SRS, median (IQR) & 2.5 & (5) \\ (PTV) & fSRS, median (IQR) & 9.3 & (17) \\ \hline Cumulative tumor volume, cc & & & \\ (\(\Sigma\)GTV) & Median (IQR) & 3.2 & (6.0) \\ \hline BED\({}_{\text{10-LQ}}\), Gy & SRS, mean (SD) & 49.37 & (10.07) \\  & fSRS, mean (SD) & 48.1 & (2.82) \\ \hline  & BED\({}_{\text{10-LQ}}\), biologically effective dose for an alpha/beta ratio of 10, linear-quadratic model; BMs, brain metastasis; DS-GPA, diagnosis-specific graded prognostic assessment; HER2, human epidermal growth factor receptor 2; HR, hormone receptor; IQR, interquartile range; KPS, Karnofsky Performance Status; NSCLC, non-small cell lung cancer; PFBMs, posterior fossa brain metastasis; SCLC, small cell lung cancer; SRS, stereotactic radiosurgery. \\ \hline \hline \end{tabular}
\end{table}
Table 1: Cont.  
Regarding the prevalence of posterior fossa BMs (PFBMs) in those according to the primary tumor (defined as those patients with at least one BM in the brainstem and/or cerebellum), it was found that patients with BMs of breast cancer were those with the highest prevalence (50%), while in those of pulmonary origin it was lower (23.2%).