## 5 Conclusions  
The aim of the present research was to estimate and characterize the entity of the displacement and deformation of the OARs surrounding the pelvic lymph node target in each treatment session with respect to the s-CT. The study showed that there is no direct relationship between the entity of the displacement of the ileum/colon and the anatomical area treated. The median displacements evaluated were 0.38 cm and 0.44 cm, respectively. These OARs resulted in the most critical structures, showing different geometrical shapes for every daily treatment fraction due to organ motion and deformation. Instead, regarding the bladder and rectum, the shape variability was mainly linked to the different daily filling and emptying statuses. As previously mentioned, the work is an ancillary study of the RADIOSA trial (AIRC IG-22159) and can be used as a benchmark for analyzing the prospective results from the trial. Based on these considerations, a further investigation must be made in order to consider the possibility of dose escalation with respect to the re-optimization of the treatment plans, exploiting the selected optimal margins for each OAR with a higher dose prescription of 45 Gy/3 fx, evaluating the constraint compliance, and paving the way for dose escalation studies. The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app122110949/s1](https://www.mdpi.com/article/10.3390/app122110949/s1)]([https://www.mdpi.com/article/10.3390/app122110949/s1](https://www.mdpi.com/article/10.3390/app122110949/s1)). Figure S1: Bladder percentage volume variation for each available CBCTs (1 to 5); Figure S2: Return percentage volume variation express as ((V_daily \(-\) Vref)/Vref) \(*\) 100 for each available CBCTs (1 to 5); Figure S3: Percentage dose varation vs. Mean_DA and DSC for each OAR. The dose percentage variation increases with increasing Mean_DA, and decreases with higher values of DSC. Conceptualization: F.L.F., G.M. ([PERSON]), G.C. and B.A.J.-F.; methodology: F.L.F., G.M. ([PERSON]), G.C. and B.A.J.-F.; software: F.L.F. and M.P. ; validation: [PERSON]. ([PERSON]), F.C. and S.C.; formal analysis: F.L.F. and M.G.V. ; investigation: [PERSON], M.A., G.C.M., C.F. and S.C.; data curation: F.A.M., S.L., S.G. and O.D.C. ; writing--original draft preparation: [PERSON], M.G.V., M.P. and M.Z. ; writing--review and editing: [PERSON]. ([PERSON]), [PERSON], F.C., R.O., B.A.J.-F. and S.G.; visualization: M.G.V. ; supervision: [PERSON]-F., [PERSON] ([PERSON]), [PERSON], F.C. and R.O. All authors contributed to manuscript's revision and read and approved the submitted version. All authors have read and agreed to the published version of the manuscript. [PERSON], [PERSON], [PERSON] and [PERSON] were supported by a research fellowship from the Associazione Italiana per la Ricerca sul Cancro (AIRC), entitled \"Radioablation \(\pm\) hormonotherapy for prostate cancer oligoccurrences (RADIOSA trial): potential of imaging and biology\", registered at ClinicalTrials.gov NCT03940235 and approved by the Ethics Committee of IRCCS, Istituto Europeo di Oncologia and Centro Cardiologico Monzino (IEO-997). IEO, the European Institute of Oncology, is partially supported by the Italian Ministry of Health (through the \"Ricerca Corrente\" and \"5x1000\" funds) and by an institutional grant from Accuray Incorporated, Medical Equipment Manufacturing, Sunnyvale, CA, USA. The study was part of general SBRT and image-guided RT research reported to the Ethical Committee of the IEO (notifications 79/10, 86/11, 87/11, and 93/11). Written informed consent to publish this paper was obtained from the patients. Not applicable. References: B.A.J.F.