## 3 Results  
A total of 25 patients with 43 spinal metastases were treated with robotic SBRT between July 2011 and January 2017. Patients had a median age of 56 years (range: 28-80), and an adequate Karnofsky performance status (KPS) (mean = 90%). The most common histologies of primary tumors were breast (32.6%), prostate (21%), lung (14%), and colorectal carcinomas (7%). Most participants (74.4%) were treated due to an adenocarcinoma. Patients were mostly naive to systemic treatment (79% of the sample). Moreover, 58% of participants received at least a first-line chemotherapy treatment. Baseline patient characteristics areshown in Table 1. The frequency of vertebral bodies involved is shown in Table 2, which shows that some of the treatments administered involved more than one vertebra. The median time from cancer diagnosis to bone metastasis was 47.76 months (range 0-154.1). The median follow-up for pain control was 15.17 months (range 0.2-85.18). Regarding RT toxicity, only one patient experienced grade III dermatitis. No other participant reported RT toxicity. Pain levels did not differ significantly between time points, as assessed by clinicians \(\chi\)2 (2) = 1.06, \(p\) = 0.60. However, VAS scores significantly decreased between \begin{table}
\begin{tabular}{c c c} \hline \hline  & **Number** & **Percentage (\%)** \\ \hline \multicolumn{3}{c}{**Age**} \\ \hline Years old (median) & 56 (28–80) & \\ Sex & 11 & 44 \\ Male & 14 & 56 \\ Female & 20 & 45.5 \\ Visceral Metastasis & 23 & 53.5 \\ \multicolumn{3}{c}{Visceral Metastasis Localization} \\ Lung & 8 & 18.2 \\ Cerebral & 4 & 9.1 \\ Nodes & 1 & 2.3 \\ Multiple localizations & 7 & 15.9 \\ Histology & & \\ Breast cancer & 14 & 32.6 \\ Prostate cancer & 8 & 18.6 \\ Lung cancer & 6 & 13.9 \\ Colorectal cancer & 3 & 7 \\ Other & 12 & 27.9 \\ Bone Metastases & & \\ Single & 8 & 18.6 \\ Multiple (\textless{}5 lesions) & 35 & 81.4 \\ Prior to CT & & \\ No & 18 & 42 \\ Yes & 25 & 58 \\ Initial KPS Index & & \\ Mean & 88.14 (SD 10.29) & - \\ Prior to RT in Other Locations & & \\ No & 36 & 83.7 \\ Yes & 7 & 16.3 \\ Infield Prior to RT & & \\ No & 35 & 81.4 \\ Yes & 8 & 18.6 \\ Spine Surgery Prior to RT & & \\ No & 34 & 79 \\ Yes & 9 & 21 \\ \hline \multicolumn{3}{c}{RT: radiotherapy; CT: chemotherapy} \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Patient characteristics. \begin{table}
\begin{tabular}{c c} \hline \hline \multicolumn{1}{c}{**Location of Spine Metastasis**} & **N\({}^{\text{o}}\)** \\ \hline Cervical & 8 \\ Thoracic & 21 \\ Lumbar & 13 \\ Sacral & 1 \\ Total lesions & 43 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Frequency of vertebral bodies affected. assessment points, t (28) = 4.14, \(p\) \(<\) 0.01, [PERSON]'s d = 0.72. SBRT treatment features are displayed in Table 3.  
Table 4 displays the statistics derived from studying univariate relationships between the pain outcomes and the variables of interest. Regarding the clinician assessment of pain at the first follow-up, despite two factors being univariately significant (the time from bone metastasis to SBRT initiation and prescribed dose), none of them showed a significant effect. Four covariates were univariately associated with the clinician's assessment at the last follow-up point: female gender (OR = 1.43); histology (OR = 1.59)--observation of higher pain scores in patients with other malignant tumors (compared to adenocarcinomas); absence of visceral progression (OR = 0.68); and lack of previous surgery (OR = 0.65). All these covariates were entered into a multivariate regression model. This model (AIC = \(-\)607.91) fitted the data better than a model without covariates (AIC = \(-\)590).