Immunotherapy is set to become the default treatment for the vast majority of lung cancer patients after a clinical trial from drugmaker Merck showed that adding its novel medicine to chemotherapy boosted survival.

Unlike traditional cancer drugs, immunotherapies work by encouraging the body’s immune system to attack tumours. They have been hailed as one of the biggest advances in decades.

Some recently diagnosed lung cancer patients already receive immunotherapy known as a checkpoint inhibitor if their tumours have high levels of the PDL1 protein. But the standard treatment is still chemotherapy. That looks set to change after the publication of a large, late-stage clinical trial yesterday in Chicago at the annual meeting of the American Association of Cancer Research. It showed that combining chemotherapy with Keytruda, Merck’s checkpoint inhibitor, significantly increased survival rates for those with the most common type of the illness, non-squamous, non-small cell lung -cancer (NSCLC).