Radiotherapy is a common and effective treatment for non‑small cell lung cancer (NSCLC) when the cancer is still contained within the chest. It is used with the aim of curing the cancer or helping people live longer. However, in many patients the cancer can return after treatment.

Radiotherapy works by damaging the DNA inside cancer cells, which usually causes them to die. Normal, healthy cells are better at repairing this DNA damage, but cancer cells can sometimes repair themselves too. If we can stop cancer cells from repairing their DNA, radiotherapy may work even better.

This study is testing a group of new drugs called DNA damage response inhibitors (DDRi). These medicines interfere with the cancer cells’ ability to repair DNA damage. We hope that giving a DDRi drug together with radiotherapy will make the treatment more effective.

Because this approach is new, we first need to find the safest and most effective dose of the drug when it is combined with radiotherapy.

We are running a clinical trial for patients who are already due to have radiotherapy, with the aim of curing the cancer or extending life. Patients who join the study will:

• Receive their standard radiotherapy, as planned.
• Receive either radiotherapy alone or radiotherapy plus one DDRi drug.
• Know in advance whether they will receive a DDRi drug, and which one. Doctors will know this too.

During and after treatment, we will follow patients closely to monitor side effects, check how the cancer is responding, and learn more about how the combined treatment works. We will also take blood samples to track progress and to help us understand which patients are most likely to benefit from this type of therapy