## 4 Discussion
Compared to more aggressive surgical methods, the concept of separation surgery, combined with advancements in RT and the utilization of SBRT for treating spinal metastases, has demonstrated promising outcomes. This approach aims to achieve effective LC while minimizing surgery-related complications and morphologies [36]. It is important to treat patients before the onset of symptoms, such as pain. Moreover, our patients had a low initial pain assessment, with a mean VAS of 2.48, and 17 lesions were asymptomatic. In addition, SCC could appear to make surgery necessary. If surgery is required, it should be minimally invasive surgery (MIS) so that robotic SBRT can be administered within 7-10 days. In our study, three factors were associated with improved pain control using SBRT: female gender, adenocarcinoma tumor type, and lack of previous surgery. Notably, this finding reinforces the concept of initiating SBRT treatment promptly upon diagnosis. In addition, patients who are asymptomatic exhibit better tolerance to SBRT treatments. The duration of these treatments typically ranges between 30 and 45 min, depending on the lesion size and the number of beams utilized. Notably, the introduction of more advanced Cyberknife(r) S7 technology is expected to further reduce treatment time to just 15 min, significantly enhancing patient comfort during the procedure. Survival expectancy is one of the main selection criteria when considering surgery in a patient. Multiple prognostic scoring scales exist to help clinicians determine post-operative life expectancy (Takuhashi, Sioutos, van der [PERSON], Tomita, and Bauer scales). In general, patients with a life expectancy of less than three months should be treated non-surgically, as the morbidity associated with surgical treatment outweighs the potential therapeutic benefits. However, MIS reduces morbidity and surgery may become an option in patientsfor whom conventional approaches are considered too morbid [1]. Specifically, in our series, 7 patients were operated on with 12 different interventions per location. Predictive factors described in the literature that may influence local control include spinal instability after surgery, large tumor volumes, and non-elevated BEDs. Other factors that may influence SBRT failure include adjacent bone, epidural space, and paraspinal tissue involvement. These factors increase treatment volume and thus result in an increased risk of recurrence. Epidural involvement may decrease overall survival and local control, and paraspinal involvement predicts recurrence and worse local control [18]. In our series, the response to SBRT was better in the non-surgical group. Obviously, surgical treatment causes acute bone and nerve trauma that may increase pain. On the other hand, surgery is also indicated because compressed nerve tissue could be relieved. Although a subgroup analysis could be very interesting, the small number of patients with surgery (only nine in our series) makes its elucidation negligible. The location of spinal metastases is also important, as cervical metastases are more painful than dorsal, lumbar, and sacral metastases. And, for example, sacral metastases respond worse than thoracolumbar metastases due to lesions with >2 vertebrae and epidural and paraspinal involvement [18]. In our series, we only treated one patient with sacral metastases, making it irrelevant to assess/support this result. It would also be interesting to know if pain correlates with tumor location (vertebral body, vertebral arch, intraspinal parts), but this was not recorded in our series. Contouring of patients' lesions following expert consensus, both operated and non-operated lesions, is essential to treat patients correctly. Several articles with recommendations for contouring metastatic spinal lesions can be found in the literature [26; 37; 38; 39]. Especially when the treatment is performed in a single session, the time patients must spend on it is obviously reduced. This is very important for patients with palliative care.