Scientists in Oxford have discovered that using an old anti-malaria drug alongside radiotherapy treatment helps shrink hard-to-treat tumours.

The drug, Atovaquone, is a cheap, widely available and safe medication which causes tumours to process oxygen differently making them sensitive to the effects of radiotherapy.

Radiotherapy works by damaging the DNA of cancer cells. But many cancers such as lung, bowel and brain tumours do not respond to radiotherapy because they have low levels of oxygen. The lower the level of oxygen the easier it is for cancer cells to repair themselves from the damage caused by radiotherapy.

Atovaquone increases the levels of oxygen in cancer cells and therefore makes it harder for them to repair the damage from radiotherapy, according to Cancer Research. As a result, scientists have seen tumours shrink in a trial involving mice and are now embarking on a clinical trial involving patients in Oxford to see if the same results will be duplicated in real patients.

Lead author, Professor Gillies McKenna, at the Cancer Research UK/Medical Research Council Institute for Radiation Oncology in Oxford, said: “This is an exciting result. We have now started a clinical trial in Oxford to see if we can show the same results in cancer patients. We hope that this existing low-cost drug will mean that resistant tumours can be re-sensitised to radiotherapy. And we’re using a drug that we already know is safe.”