# Volumetric Modulated Arc Therapy for Radiosurgery of Brain Metastases: A Single-Center Study
## 4 Discussion  
VMAT radiosurgery for the treatment of BMs is increasingly utilized in radiotherapy treatments due to its high level of efficiency compared to other intensity-modulated radiotherapy techniques [22]. Several previous studies analyzed dosimetric parameters \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Hazard Ratio** & **95\% CI** & _p-Value_ \\ \hline
**Univariate** & & & \\ \hline KPS & & & \\ KPS \(\geq\) 70 & 1 & & \\ KPS \(<\) 70 & 4.153 & 2.728–6.322 & \(<\)0.001 \\ \hline DS-GPA Class & & & \\ Class I (0–1.0) & 1 & & \\ Class II (1.5–2.0) & 0.583 & 0.373–0.911 & 0.018 \\ Class III–IV (2.5–4.0) & 0.319 & 0.199–0.511 & \(<\)0.001 \\ \hline Age & & & \\ \(<\)65 years & 1 & & \\ \(\geq\)65 years & 1.596 & 1.101–2.316 & 0.014 \\ \hline Posterior fossa BMs & & & \\ No & 1 & & \\ Yes & 0.616 & 0.396–0.956 & 0.031 \\ \hline Primary tumor type & & & \\ Lung & 1 & & \\ Breast & 0.505 & 0.289–0.885 & 0.017 \\ \hline Epilepsy-related brain tumor & & & \\ Yes & 1.010 & 0.681–1.499 & 0.959 \\ No & 1 & & \\ \hline Cumulative brain tumor & & & \\ EGTV \(\geq\) 5 cc & 1.292 & 0.878–1.900 & 0.194 \\ EGTV \(<\) 5 cc & 1 & & \\ \hline Extracranial metastases & & & \\ Yes & 1.225 & 0.844–1.778 & 0.286 \\ No & 1 & & \\ \hline Multivariate & & & \\ KPS & \(\geq\) 70 & 1 & \\ KPS \(<\) 70 & 2.593 & 1.484–4.532 & 0.001 \\ \hline DS-GPA Class & & & \\ Class I (0–1.0) & 1 & & \\ Class II (1–5.2–0) & 0.548 & 0.328–0.915 & 0.022 \\ Class III–IV (2.5–4.0) & 0.378 & 0.189–0.756 & 0.006 \\ \hline Age & & & \\ \(<\)65 years & 1 & & \\ \(\geq\)65 years & 0.714 & 0.433–1.178 & 0.187 \\ \hline Posterior fossa BMs & & & \\ No & 1 & & \\ Yes & 0.646 & 0.378–1.102 & 0.109 \\ \hline Primary tumor type & & & \\ Lung & 1 & & \\ Breast & 0.731 & 0.403–1.327 & 0.303 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Univariate and multivariate analysis of prognostic factors. and procedure times, showing how the use of non-coplanar VMAT arcs presents high levels of dose conformality with low levels of exposure of healthy brain parenchyma [23] as well as reduced procedure times [9; 11]. Another advantage shown by SRS over conventional WBRT is the lower neurocognitive impact on treated patients [7; 8], an aspect of growing interest given the increased life expectancy of patients. However, at present, many questions remain to be resolved regarding survival, such as the potential impact of the location of BMs, the tumor burden, or the presence of tumor-related epilepsy, among others. This is one of the first studies to analyze holistically a cohort of patients with BMs treated with radiosurgery using volumetric modulated arc therapy, trying to offer a global radiography of the neuro-oncologic patient by analyzing both the main radio-oncologic and clinicopathologic variables. Firstly, the most frequently found primary tumor in this cohort was lung cancer (67.8%), followed by breast cancer (13.2%), similar to previously reported [24]. Regarding sex distribution, the prevalence of men was higher than women in the cohort, also partly due to the higher prevalence of the male sex in the cohort of lung cancer patients (74.4% versus 25.6%, \(p<0.001\)). Our study also showed that patients with breast cancer and melanoma were younger than those with gastrointestinal cancer or prostate tumors (\(p=0.006\)). Regarding the distribution of the BMs, the frontal lobe (34.9% of the BMs) was the main location of the BMs, similar to previous works [25]. In contrast, only 16.1% of the BMs were in structures of the posterior fossa of the CNS (brainstem and/or cerebellum), with breast cancer metastases being the most frequent in this latter location. Several studies have found that the cerebellum is the predominant site of metastases in breast cancer patients [11; 26; 27; 28; 29].