The PRECISION Study: A Phase II Study of 3 Fractions of Prostate SBRT With RayPilot System and HypoCath Image Guidance for Men With NCCN Low or Intermediate Risk Prostate Cancer

Prostate cancer is the commonest male cancer and sadly more than 10,000 men die each year from the disease in the UK. This is actually a greater number than women who die from breast cancer each year in the UK. If diagnosed at an early stage, the chances of being cured of the disease are high through either surgery (prostatectomy) to remove the prostate or through radiation treatment (radiotherapy). Both treatment options are associated with quality of life changing impacts on sexual, bowel and bladder function, with survivors having to manage these side effects for the rest of their lives. It is a key area of research to try and identify who may be at particular risk and to minimize these risks. The development of increasingly sophisticated radiotherapy machines (linear accelerators) which can deliver radiotherapy more precisely has allowed the radiotherapy for prostate cancer to be transformed over the last decade. The number of treatments required for cure has been reduced from 39 over nearly 8 weeks, to 20 over 4 weeks, and more recently to only 5 over 1-2 weeks, greatly improving patient convenience through less travel, days off work, or time in hospital away from loved ones. Importantly technology has reduced but not removed the risk of both initial and then longer term permanent side effects.

In this study the investigators want to reduce the number of treatments down to only 3, given on consecutive days, further enhancing the patient experience and providing evidence that this number of treatments could become the new standard of care. In this study the investigators will be using the very latest state of the art radiotherapy machines and the unique RayPilot system, adopted for routine use by a small number of global radiotherapy centres when delivering prostate SBRT(Stereotactic Body Radiotherapy). The ability to track the position of the prostate cancer throughout the radiotherapy treatment using RayPilot allows the treatment to be given more precisely with less dose being given to the surrounding bladder and rectum. It also ensures that all the intended dose is given to the cancer as the treatment can be interrupted should the cancer move due to rectal gas, changes in bladder filling or simply the patient moving position on the treatment bed, maximizing the chances of cure and minimizing the risk of life changing side effects.

This is a single arm 2 stage Phase II study that will test the safety of the 3 fraction radiotherapy schedule. It has built in safety measures to ensure that the immediate post treatment side effects on the bowel and bladder are within the expected limits of acceptance at 12 weeks post completion of treatment. After 43 patients are recruited the initial data will be analyzed and if acceptable the study will continue until all 100 patients have been recruited. The study will be opened in the UK with Edinburgh as the lead Centre, and also in a number of other global centres each of which will ask for their own local ethical approval and sponsorship. The anonymized data from each Centre will be recorded on a trial specific RedCap database held by the University of Edinburgh for analysis of the trial results.

On the day of treatment planning, the patient will be met by the research team and taken to the MRI suite. Patients will have already have been prescribed a rectal suppository by their GP to bring with them. The patient will be directed to the toilet at the MRI scanner and will pass the suppository into their rectum and wait 30 seconds before evacuating it. The aim is to dispel rectal gas not necessarily to move the bowels. Patients will also empty their bladder of urine. The research nurse or radiographer will then place a dummy RayPilot HypoCath (called a ViewCath) or a simple standard Foley urinary catheter if preferred, and fill the bladder with 100-150 mls of water. This volume is recorded and kept as a constant for each day of subsequent treatment. An MRI of the prostate is then performed with standard T1 and T2 anatomical images and functional Dynamic Contrast Enhanced (DCE) and diffusion weighted (DW) sequences that identify the tumour. The MRI scan will last approximately 20minutes. On completion the patient is then taken for the planning CT scan within the Radiotherapy Department. The bladder is drained and then refilled through the catheter to the same volume as the MRI scan. The suppository is only repeated if there has been a substantial change in the rectal volume between the MRI and planning CT scan. The CT scan takes 15 minutes and then the patient has the catheter removed and is free to go home.

The MRI and CT scan are fused together to allow the clinician to plan the radiotherapy treatment on the radiotherapy planning computer system. Once the target and surrounding normal tissues have been outlined and a radiotherapy plan developed then the patient is ready to start treatment. The planning of treatment takes 2 weeks on average.