The PEARLS study is designed to find out whether treating a larger area with radiotherapy can improve outcomes for people with prostate cancer that has spread to the lymph nodes in the abdomen.

At the moment, there is no standard treatment for patients who are diagnosed with prostate cancer that has already reached these lymph nodes. Previous research has shown that it is safe to treat the prostate and the lymph nodes in the pelvis with radiotherapy. However, modern radiotherapy techniques have not yet been tested on a wider area that includes the lymph nodes higher up in the abdomen. Treating this area may help reduce the chance of the cancer coming back.

PEARLS will compare:

• Standard radiotherapy, which targets the prostate and pelvic lymph nodes
• Extended‑area radiotherapy, which also includes lymph nodes in the abdomen where the cancer may spread

The main aim is to find out whether the extended treatment:

• Is safe and has acceptable side‑effects
• Can help improve cancer control

• PEARLS will recruit 893 patients whose prostate cancer has spread to the lymph nodes.
• At first, the safety of the extended treatment will be checked in the first 150 patients. If the side‑effects are too severe, the study may stop early.
• Patients will be randomly assigned to either the standard or extended radiotherapy group, based on how much cancer is seen in their lymph nodes.
• All patients will receive radiotherapy over 20 treatment sessions (fractions).
• Patients will be followed up regularly after treatment to check how they are doing.
• Throughout the study, patients will be asked to complete quality‑of‑life questionnaires.

Some patients may be invited to take part in extra research within PEARLS, which may include:

• Giving blood samples
• Giving a stool (poo) sample
• Having an extra PSMA PET‑CT scan about 6 months after radiotherapy or if their cancer comes back

These extra tests are optional.