A major development in prostate cancer treatment has been presented at the Congress of the European Society for Radiotherapy and Oncology (European Society for Radiotherapy and Oncology 2026). Early results from the HERMES clinical study suggest that prostate cancer patients may be safely treated with just two high dose radiotherapy sessions instead of the current standard of five, without increasing side effects.
This finding could significantly change how radiotherapy is delivered in the future, making treatment faster, more convenient, and potentially more efficient for healthcare systems. The study was led by researchers from The Royal Marsden NHS Foundation Trust and the Institute of Cancer Research, two leading UK institutions in oncology research.
The HERMES study is one of the first randomized clinical trials to directly compare two different radiotherapy schedules for localized prostate cancer:
A total of 46 patients participated in the study. Of these, 24 received the standard five session treatment, while 22 received the two session high dose approach.
Researchers aimed to determine whether reducing the number of hospital visits while increasing the dose per session would remain both safe and effective, particularly in terms of urinary, bowel, and overall quality of life outcomes.
A key factor enabling this approach was the use of advanced MRI guided radiotherapy technology. This system combines magnetic resonance imaging with a radiotherapy delivery machine, allowing clinicians to precisely target the prostate while minimizing radiation exposure to surrounding healthy tissue.
This level of precision is essential when delivering higher doses in fewer sessions, as it reduces the risk of damaging nearby organs such as the bladder and rectum.
The study results showed that two-session radiotherapy was feasible and did not lead to increased side effects compared with the standard five-session approach.
According to the research team, around one in four patients in both treatment groups experienced moderate urinary side effects, such as increased frequency or urgency. Importantly, there were no severe urinary or bowel side effects reported in either group.
Bowel side effects were extremely rare overall, and notably, none of the patients in the two-session group reported bowel-related complications.
After two years of follow-up, patients in both groups reported minimal changes in quality of life. There was no meaningful difference in long-term side effects between the two treatment schedules.
Dr Sian Cooper, Clinical Research Fellow at The Royal Marsden NHS Foundation Trust and the Institute of Cancer Research, explained the motivation behind the study:
Radiotherapy is a key curative treatment for prostate cancer, and most patients currently receive five treatment sessions. However, there has been growing interest in hypofractionation, which means delivering higher doses per session over fewer visits.
The goal of the HERMES study was to determine whether two sessions could safely replace five without increasing side effects such as urinary or bowel dysfunction.
Dr Cooper highlighted that shorter treatment schedules could have major benefits for patients, including less disruption to work, travel, and family life. It could also improve hospital efficiency by allowing more patients to be treated in less time.
Professor Matthias Guckenberger from University Hospital Zurich and President of ESTRO, who was not involved in the study, commented on the significance of the findings.
He noted that radiotherapy is already a highly effective, non invasive treatment for prostate cancer that helps preserve quality of life by minimizing damage to surrounding organs.
He also explained that shorter treatment schedules have long been considered but were previously thought to require careful validation to ensure they were equally effective and safe.
According to his assessment, this study provides reassuring evidence that fewer, higher dose treatments may maintain cancer control while keeping side effects low.
He also pointed out that reduced treatment schedules could make radiotherapy more accessible, especially for patients living far from treatment centers, and may reduce costs for healthcare systems.
If confirmed in larger trials, this approach could represent a meaningful improvement in prostate cancer care.
While the results are promising, researchers emphasize that this is still an early stage clinical study involving a relatively small number of patients. Larger trials with longer follow up are needed before changing standard clinical guidelines.
However, the combination of strong safety data and modern imaging guided radiotherapy technology suggests that further adoption of ultra hypofractionated treatment schedules is likely.
As MRI guided radiotherapy becomes more widely available across specialist cancer centers, the feasibility of implementing two session treatment protocols may increase.
This breakthrough study presented at ESTRO 2026 indicates that:
The HERMES study represents an important step forward in prostate cancer radiotherapy research. While more evidence is needed before widespread adoption, the results suggest that treatment could soon become faster and more patient friendly without compromising safety.
If confirmed in larger studies, two session radiotherapy may reshape standard care for localized prostate cancer and improve both patient experience and healthcare efficiency.
This article is based on findings presented at the European Society for Radiotherapy and Oncology (European Society for Radiotherapy and Oncology) 2026 Congress, including data from the HERMES clinical study conducted by researchers from The Royal Marsden NHS Foundation Trust and the Institute of Cancer Research.
This blog post is for informational and educational purposes only. It is based on early clinical research findings and should not be considered medical advice. Treatment decisions for prostate cancer should always be made in consultation with qualified healthcare professionals. Results from early studies may not always reflect final clinical guidelines, and further large scale research is required before changes to standard treatment protocols are confirmed.
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