Protons vs. Photons for High-risk Prostate Cancer

Proton therapy (PT) is a radiation technique with possibility to spare normal pelvic organs: bladder, rectum and bowel for PC patients. Most PC patients treated with PT receive PT to the prostate gland alone. With PT, we aim to examine PC patients in high risk with both lymph node and prostate treatment will experience less late side effects with PT compared to photon treatment. The investigators propose a national open-labelled phase III randomized controlled trial (RCT) of proton therapy versus photon therapy of the prostate including the regional elective LN for localized/locally advanced prostate cancer patients combined with androgen deprivation therapy (ADT) aimed at 3 years. The investigators aim at reducing gastro-intestinal toxicity grad 2 more than 5 points, which is considered clinical significant, measured by mean Expanded Prostate Cancer Index Composite-26 (EPIC-26) bowel scores at 24 months and improve HRQOL. Secondary endpoints include morbidity, quality of life and survival data up to 10 years after treatment. Update August 2026: The primary endpoint has been updated. To consider a more meaningful clinical endpoint the investigators have decided to update the endpoint and look at a 10 points difference in EPIC-26 bowel score at 24 months follow-up instead of a 5 points difference. A new power-calculation was made based on the same assumptions and the total number of patients was changed from 400 to 102.