Hypofractionated Expedited Radiotherapy for Men With localisEd proState Cancer

The purpose of this research is to investigate whether stereotactic body radiotherapy (SBRT), precise X-ray treatment, is best given in five treatments (also called fractions) over 10 days or in two treatments over 8 days. SBRT is an accurate way to deliver a high dose of radiotherapy to the prostate in a smaller number of doses. We have considerable experience with 5-dose SBRT and now wish to examine the feasibility and safety of delivering treatment over two, larger, doses. Previous work has shown it is theoretically possible to deliver two fraction SBRT on the MR-linac and previous studies have shown internal radiotherapy (brachytherapy) administered in two fractions to be a safe option for patients with low-risk prostate cancer. All treatment within this trial will be delivered on a new, state of the art, radiotherapy machine called an MR-linac (Magnetic Resonance Linear Accelerator). It puts together an MRI scanner with a radiotherapy treatment machine called a Linear Accelerator. The use of the MR-linac means there is no extra radiation dose given when taking images (unlike computerized tomography (CT) scans or X-ray), enabling us to adapt the radiotherapy plan each day if needed to more precisely target the prostate. The results of the study will enable us to find out if the new, shorter treatment (2 doses of radiotherapy), has a similar level of side effects as the 5 dose treatment and is suitable for further study.