Prostate cancer study aims to find gentler radiation option

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: * Men aged ≥18 years at randomisation * The research subject must have capacity to sign a written informed consent document for the trial * WHO performance status 0 - 2 * Gleason score 3+3 or 3+4 * PSA ≤ 20 ng/ml (please note if the treating clinician determines androgen deprivation therapy (ADT) is required this is an exclusion criteria). A PSA must be available within 60 days of randomisation. * Clinical and/or MRI stage T1c -T2c, N0-X, M0-X * Histological confirmation of prostate adenocarcinoma within the last 18 months (unless on active surveillance). Patients who were on active surveillance should have an up-to-date MRI within 8 weeks of the decision to treat to confirm organ confined disease. Exclusion Criteria: * Previous malignancy within the last 2 years (except basal cell carcinoma or squamous cell carcinoma of the skin), or if previous malignancy is expected to significantly compromise 10-year survival. * Patients under investigation for synchronous primary at time of randomisation * Prior pelvic radiotherapy. * Prior treatment with ADT or current need for ADT based on risk features * Prostate cancer in greater than 50% of template biopsy cores or a significant maximum core length containing prostate cancer for which the treating clinician deems the patient would benefit from ADT * Any prior active treatment for prostate cancer (patients previously on active surveillance are eligible if they meet all other eligibility criteria) * Life expectancy \< 10 years Men with a prostate gland larger than 60 cc, or those with a large median lobe• Hip prostheses or any other implants/hardware that introduce substantial CT artefacts making it challenging to delineate the target or organs at risk. This is to be assessed on a case-by-case basis with the available staging imaging. * Medical conditions likely to make radiotherapy inadvisable e.g. inflammatory bowel disease, significant urinary symptoms. * International Prostate Symptom Score (IPSS) \> 15 points * Anticoagulation with warfarin/ bleeding tendency making fiducial placement, spacer gel insertion or brachytherapy unsafe in the opinion of the clinician * Contraindications for Barrigel insertion such as previous documented allergic reaction to gel, previous rectal surgery or known rectal fistula. * Participation in another concurrent treatment protocol for prostate cancer.