The study focuses on the scientific and clinical evaluation of online adaptive radiotherapy (ART) using the Varian/SHS ETHOS treatment system. In this study, radiation treatment plans are dynamically adjusted on a daily basis over several weeks of therapy to account for anatomical shifts in either the tumour or adjacent normal tissue - a capability that has been difficult to achieve due to technical limitations. With the ETHOS accelerator, such real-time adjustments can be made based on cone beam computed tomography (CBCT). This is a prospective observational study with the primary objective of investigating the feasibility and acceptability of performing ART with ETHOS for different tumour entities. The study will also evaluate the feasibility of integrating multi-parametric data sets into the ART workflow, such as standardised electronic feedback on treatment toxicity from both patients (ePROMS) and physicians (ePRT).