Doctors have hailed a "spectacular" breakthrough in cancer treatment after a pair of drugs were found to shrink tumours in nearly 60% of people.
A British-led trial on 945 patients with advanced melanoma found treatment with immune-boosting drugs - ipilimumab and nivolumab - stopped the cancer advancing for nearly a year in 58% of cases.
Melanoma is the most serious form of skin cancer and kills more than 2,000 people in Britain each year.
Immunotherapy harnesses the body's immune system to attack cancerous cells.
Experts say the treatment may bring about a "whole new era" for successful cancer care.
The so-called "double hit" treatment helped shrink tumours or bring them under control in 58% of people with advanced melanoma - allowing patients to live 11.5 months without tumours growing.
When just ipilimumab was used, tumours stayed stable or shrunk in just 19% of cases for an average of 2.5 months.
Professor Roy Herbst, chief of medical oncology at Yale Cancer Centre in the US, described the findings as "spectacular" and said immunotherapy could replace chemotherapy as the standard treatment for cancer within the next five years.
Dr James Larkin, a consultant at the Royal Marsden Hospital, told the 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."
He added: "For immunotherapies, we've never seen tumour shrinkage rates over 50% 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."
Dr Alan Worsley, Cancer Research UK's senior science information officer, said the "powerful one-two punch" treatment could "block cancer's ability to hide" from the immune system.
"It has given me my life back"
Cait Chalwin, 43, was given between 18-24 months to live when doctors diagnosed her with melanoma in 2013.
Ms Chalwin, from Cornwall, was referred to the Royal Marsden Hospital where she started on the nivolumab/ipilmumab trial.
Her cancer is now stable, however she has now come off the trial due to side affects.
She goes back to the Royal Marsden every three months for a scan.
"I am feeling absolutely amazing now. It took a long time to get back to normal, to feel how I felt before diagnosis, however I do firmly believe that if the treatment hadn't worked, I wouldn't be here now.
" At diagnosis I was given 18-24 months to live, and this trial was my only hope - but it has given me my life back."