"This study highlights the importance of understanding the genetics of cancer to achieve therapeutic benefit. It will enable clinicians to select which patients they administer these drugs to, allowing them to personalise treatment for each patient. This research also provides the springboard for developing drugs that will work in patients whose tumours carry a faulty RAS gene."

Dr Lesley Walker, director of cancer information at Cancer Research UK, said: "These findings provide an important insight into the genetic mechanisms of human cancer. They show how basic scientific research is vital to clinical care and emphasise the importance of understanding the makeup of individual cancers when using new targeted treatments of this type.

"The impact of this research will enable doctors' testing BRAF inhibitors in the clinic to target the treatments more precisely to patients who will definitely benefit, and avoid treating those who won't."