Cutaneous squamous cell carcinoma (cSCC) is a common type of skin cancer. Most people are cured with surgery. However, in some cases the cancer can come back in the same area or in nearby lymph glands. This is more likely to happen when the original cancer was large, had grown along nearby nerves, or had spread deeper into the tissues under the skin. These types of cancers are called high‑risk cSCCs, and about 1 in 3 of them may return.

When cSCC comes back, it can have a big impact on a person’s daily life and wellbeing. Sometimes cancer returns because a small number of cancer cells were left behind at the time of surgery, even though this was not known at the time, or because cancer cells had already started to spread into the surrounding skin.

Radiotherapy is sometimes used after surgery to try to kill any remaining cancer cells. However, we do not yet know for sure whether radiotherapy actually reduces the risk of the cancer returning. Even so, some hospitals within the NHS already offer radiotherapy for high‑risk cSCC after surgery.

This study aims to find out whether radiotherapy is helpful and whether it is better than not using radiotherapy for preventing high‑risk cSCC from coming back.

After surgery, people who take part in the study will be randomly placed into one of two groups:

• Radiotherapy plus regular follow-up
• Regular follow-up only

Both options are already used in the NHS.

Participants will be closely monitored for any signs of the cancer returning, as well as for treatment side effects and changes in quality of life.

If the results show that radiotherapy is effective, it could become a routine NHS treatment for people with high‑risk cSCC. The study will involve about 840 patients across 25 centres in the UK.