This study will ultimately aim to evaluate the side effects of treatment by asking 20 subjects to receive post-operative radiotherapy for prostate cancer with the treatment plan adapted after the first week of treatment to account for changes in the target shape. These patients will be asked to complete toxicity scores and a quality of life questionnaire at the start and completion of treatment, and at 3 months 1, 2 and 5 years from the start of radiotherapy. These results will be used to determine the feasibility of the proposed approach, and obtain early estimates of improvements in uncertainty margin requirements for this population of patients.