A "milestone" trial has shown that a lung cancer therapy can more than double life expectancy in some patients.

Nivolumab stops cancerous cells hiding from the body's own defences, leaving the cancer vulnerable to attack.

Presented  by pharmaceutical company Bristol-Myers Squibb at the American Society of Clinical Oncology, results from 582 people were showcased and described as "giving real hope to patients".

Nivolumab, one of a suite of drugs called "checkpoint inhibitors" being developed by pharmaceutical companies stops cancers from turning off the immune system so the body can keep on attacking the tumour.

The trial was conducted in Europe and the US on patients who had advanced lung cancer and who had already tried other treatments.

According to BBC, people on standard therapy lived for another 9.4 months at this stage, but those taking Nivolumab lived for 12.2 months on average.

However, some patients did spectacularly well. Those whose tumours were producing high levels of PD-L1 lived for another 19.4 months.

Lead researcher Dr Luis Paz-Ares, from the Hospital Universitario Doce de Octubre in Madrid,Spain, said "the results] mark a milestone in the development of new treatment options for lung cancer."

It is hoped the drugs will work in a range of cancers, even as  Nivolumab has already been approved in the US for melanoma.

There are however a few unanswered questions like the long-term consequences of modifying the immune system and the best way of figuring out who will respond to therapy is uncertain.