A pair of cancer drugs which harnesses the power of the immune system can shrink tumours in nearly 60 per cent of patients with advanced melanoma - the deadliest form of skin cancer, a new global trial has found.

The British-led trial on 945 patients found treatment with ipilimumab and nivolumab stopped the cancer advancing for nearly a year in 58 per cent of cases. UK doctors presented the data at the American Society of Clinical Oncology in Chicago. Cancer Research UK said the drugs deliver a "powerful punch" against one of the most aggressive forms of cancer. Melanoma, the most serious form of skin cancer, is the sixth most common cancer in the UK – it kills more than 2,000 people in Britain each year.

Harnessing the immune system is a rapidly developing field in cancer research. The immune system is a powerful defence against infection. However, there are many "brakes" built in to stop the system attacking our own tissues. Cancer - which is a corrupted version of healthy tissue - can take advantage of these brakes to evade assault from the immune system.

The study has been published in the 'New England Journal of Medicine'. James larkin, a consultant at the Royal Marsden Hospital and one of the UK's lead investigators, told BBC: "By giving these drugs together you are effectively taking two brakes off the immune system rather than one so the immune system is able to recognise tumours it wasn't previously recognising and react to that and destroy them.

"For immunotherapies, we've never seen tumour shrinkage rates over 50 per cent so that's very significant to see.  "This is a treatment modality that I think is going to have a big future for the treatment of cancer. Both drugs were developed by Bristol-Myers Squibb," larkin said. Many pharmaceutical companies are developing similar drugs that have the same effect on the immune system. The bigger hope is these immunotherapies will prove to be effective treatments for a wide range of cancer types.