Pelvic Tumor

SBRT delivers high-dose radiation to precisely defined target volumes and is an effective locally ablative treatment option for both primary tumours and oligometastases in various settings, including lesions in the abdomen or pelvis. However, SBRT in these regions faces considerable challenges such as inter-fractional organ motion and anatomical deformation, which can compromise treatment precision. MR-guided SBRT offers a solution, providing superior soft-tissue contrast and enabling real-time, online treatment plan adaptation over the course of SBRT. This approach reduces the risk of geographical miss and overdose to adjacent, vulnerable OARs. Currently, MR-guided SBRT uses a fixed dose per fraction, only adjusting target volume and OAR contours for anatomical changes when performing plan adaptation. However, overlaps between planning target volumes (PTVs) and dose-limiting OARs regularly require compromises in PTV coverage. To address this, AF aims to also adjust dose per fraction based on daily PTV-OAR overlap. With this approach, more dose is applied on treatment days with less PTV-OAR overlap while less dose is applied on days with more PTV-OAR overlap. This trial assesses the feasibility of AF in MR-guided SBRT for abdominal and pelvic tumours that show PTV-overlap with one or more dose-limiting OARs, ultimately aiming to enhance PTV dose coverage without increasing toxicity.

This study's purpose is the comparison of the automatically segmented 3D model to the reference manual segmentation, based on the Dice precision index. It is implemented by making parents' patients, surgeons and surgical helpers answer specific questions comparing 3D images to usual 2D images of the patient's tumor.

This prospective registry-based trial will include patients with pelvic or thoracic tumors with an indication for radiotherapy treated with oART or IGRT. For the primary endpoint and the secondary clinical endpoints, the trial will compare oART versus IGRT, for technical endpoints the trial will compare the real oART scenario with two virtual (hypothetical) control scenarios. Primary endpoint: * 10% reduction in the rate of acute radiotherapy related toxicity (≥ CTCAE II°, v5.0) using oART Secondary endpoints: * Clinical endpoints: Tumor control, late toxicities compared to conventional irradiated patients, quality of life and patient-reported outcomes * Technical endpoints: Target volume, target coverage, dose to organs at risk, anatomical variability score