# Volumetric Modulated Arc Therapy for Radiosurgery of Brain Metastases: A Single-Center Study
## 4 Discussion
Although the \"seed and soil\" theory has traditionally been used to explain localization in specific areas of the brain [30], other possible explanations have now been proposed to explain the preferential involvement of the cerebellum by breast cancer BMs that include both anatomical and hemodynamic aspects [29]. Therefore, this differential CNS distribution according to primary tumor could be of importance for the planning of treatment schemes in the future. Secondly, the potential impact on the survival of brain tumor-related epilepsy patients treated with radiosurgery remains _terra incognita_ at present. The prevalence of seizures reported in previous studies ranged from 20 to 35%, being more frequent in patients with BMs of lung cancer and melanoma. Other major factors known to increase the risk of seizures would be: supratentorial and cortico/subcortical junction localization and the presence of hemorrhagic components in BMs [14; 31; 32; 33; 34; 35]. In our study, the prevalence was 30.6%, with the most frequent etiology in the overall BTRE cohort being of pulmonary origin (51.35%). Patients with melanoma BMs developed seizures most frequently (66.67%), although these results should be taken with caution given the small sample size of this subgroup of patients. Some demographic aspects have been scarcely analyzed in previous studies, and there is no clear consensus on the results obtained. Thus, while [PERSON] et al. (2020) [36] et al. reported that age is the only variable that correlates negatively with the occurrence of pre- and postoperative seizures, other authors such as [PERSON] et al. (2020) [37] and [PERSON] et al. (2022) [38] did not observe any significant correlation between age and seizure risk. In our study, no statistically significant differences were found with respect to either sex (\(p=0.061\)) or age (\(p=0.753\)). Finally, another aspect of special interest is the therapeutic management of epileptic seizures. Its importance lies in the impact that the appropriate choice of antiseizure medication has both on seizure control and on the potential impact on the neurocognitive sphere and the quality of life of patients. However, given its complexity, this topic was addressed in particular elsewhere [14; 15]. Thirdly, for the evaluation of the local response of BMs to radiosurgery treatment, the mRECIST criteria [20; 39] were used, which represent an institutional modification of the RECIST 1.1 criteria [40]. One of the main differences between the two criteria focuses on the definition of measurable lesions [20]. Thus, with the mRECIST criteria, metastatic lesions with a minimum diameter of 5 mm are included instead of 10 mm, as postulated by the RECIST 1.1 criteria [40]. This increases the potential set of BMs studied and may be more sensitive for detection of local disease progression. This is because it does not require a minimum absolute increase of 5 mm but only an increase \(\geq\) 20% in the sum of the longest diameters compared to the nadir value [20]. In our work, the mRECIST 1.1 criteria were applied individually to each BM, obtaining a local control percentage of 88.5% at a mean of 2.9 months from the date of radiosurgery (SD 1.4 months). This proportion of local control is comparable to the one obtained in our previous study, although now with a larger sample size [11]. In addition to the RECIST criteria, there are other criteria for assessing response to treatment, such as the Macdonald and BM-RANO criteria [41]. Some recent studies have observed a high degree of concordance between some of these criteria (mRECIST, RECIST 1.1, and BM-RANO) [20]. Finally, the MST from the date of radiosurgery was 7.7 months, which is comparable to the overall result obtained in the RTOG 9508 trial. These findings are also comparable to other previous studies that analyzed the survival of BM patients treated with radiosurgery, although some variability can be found in the literature: [PERSON] et al. (2014) (MST 8 months) [42], [PERSON] et al. (2015) (7.2 months) [9], [PERSON] et al.