A Study of Short-course Hypofractionated Online-adaptive Radiotherapy for the Post-operative Treatment of Endometrial Cancer: Tolerability and Feasibility

The goal of this clinical trial is to assess the safety and feasibility of using a new form of radiotherapy technology, known as CT online-adaptive radiotherapy, to reduce the number of treatment sessions required in post-operative radiotherapy for patients with endometrial cancer, from 25 sessions over 5 weeks to 5 sessions over a week and a half. The main questions it seeks to answer are: * If it is safe to deliver the radiotherapy in a smaller number of treatment sessions with a larger dose per session by utilising the CT online-adaptive technology * If it is feasible for this treatment to be delivered using the CT online-adaptive technology in a clinical trial All participants who enrol in the study would be offered the trial treatment of the radiotherapy being delivered in 5 sessions. Any potential participants who are subsequently found to be ineligible during the radiotherapy planning process would be excluded from the trial treatment of a higher dose over 5 sessions, but would still be offered the CT online-adaptive technology over 25 sessions outside of the trial. Participants would undergo the trial treatment with the radiotherapy being delivered in 5 sessions over a week and a half using the CT online-adaptive technology, with any issues during the treatment delivery recorded, and a questionnaire to complete at the end of treatment to see how the new technology was tolerated by participants. Participants will have their side effects recorded by the trial team before, during and after their treatment for 2 years following the radiotherapy. During this time period participants will also be asked to complete patient questionnaires to assess their perception of side effects and their quality-of-life after undergoing the treatment. Participants will also have blood tests before, during and after the radiotherapy for 3 months to check for any potential problems with blood counts as a result of the trial treatment. During the 2 years of follow-up after the