Treating cancers with immunotherapy and radiotherapy at the same time could stop them from becoming resistant to treatment, according to a Cancer Research.

The a new study, based at The University of Manchester and cofunded by Cancer Research and MedImmune, the global biologics research and development arm of AstraZeneca, found that combining the two treatments helped the immune system hunt down and destroy cancer cells that weren’t killed by the initial radiotherapy in mice with breast, skin and bowel cancers.

Radiotherapy is a very successful treatment for many forms of cancer, but in cancer cells that it doesn’t kill it can switch on a ‘flag’ on their surface, called PD-L1, that tricks the body’s defences into thinking that cancerous cells pose no threat.

The immunotherapy works by blocking these ‘flags’ to reveal the true identity of cancer cells, allowing the immune system to see them for what they are and destroy them. The approach improved survival and protected the mice against the disease from returning.

Dr Simon Dovedi, the lead researcher said: “Using the body’s own defences to treat cancers has huge potential with early phase clinical trials demonstrating exciting patient benefit but we are still at the early stages of understanding how best to use these types of treatments.

“Combining certain immunotherapies with radiotherapy could make them even more effective and we’re now looking to test this in clinical trials to see just how much of a difference it could make.”

Professor Nic Jones, Cancer Research UK’s chief scientist, said: “Around half of all cancer patients are given radiotherapy and it has been at the heart of helping improve survival rates so that today one in two cancer patients will survive for at least ten years. Doctors and researchers are constantly looking for ways to improve treatments and this approach could open the door to a whole new way of giving radiotherapy.”