Treating men suffering from prostate cancer with radiotherapy on top of regular treatment could extend the life of patients with advanced forms of the disease, research has suggested.
One of the largest ever clinical trials into prostate cancer found an 11% increase in the survival rate of some patients.
It showed that there could be a benefit to treating the prostate - the site of the primary tumour - with radiotherapy even if the disease has already spread, the researchers said.
Among men whose cancer had spread to their lymph nodes and/or bones close to the prostate gland who were treated with radiotherapy, around 80% survived for at least three years.
On the other hand, only 70% of men who did not have the additional radiotherapy treatment were alive after three years.
The Stampede trial opened in 2005 and has so far involved more than 10,000 participants - 2,000 of whom had advanced forms of the disease - and is based at University College London.
Of those 2,000 with advanced prostate cancer, half were given standard treatment while the other half were given standard treatment plus radiotherapy.
But the team of scientists found the benefit was unique to those whose cancer had spread to their lymph nodes and/or nearby bones, and did not appear to increase survival among men whose cancer had spread to other organs or more distant bones.
Funded by Cancer Research UK, the research suggests radiotherapy could become a standard treatment alongside hormone therapy for men with prostate cancer.
Around 47,000 men are diagnosed with the disease every year and 11,500 die of it, according to Cancer Research UK's figures.
The findings suggest that pairing radiotherapy with standard treatment could help 3,000 men each year in the UK alone.
Lead researcher Dr Chris Parker, who is based at the Royal Marsden Hospital in west London, said using radiotherapy when the cancer had already spread had previously been seen as "shutting the stable door after the horse has bolted".
He said the findings could change standards of care across the globe, adding: "Unlike many new drugs for cancer, radiotherapy is a simple, relatively cheap treatment that is readily available in most parts of the world."
Chief investigator Professor Nicholas James, of the University of Birmingham, said: "Although survival times are improving, no one with advanced prostate cancer is cured of their disease by hormone therapy alone.
Professor Charles Swanton, Cancer Research UK's chief clinician, said: "Adding radiotherapy to current treatment shows clear benefit for this subgroup of men with prostate cancer.
"We now need to investigate whether this could also work for other types of cancer. If we can understand exactly why these men benefit from the additional radiotherapy treatment, we could hopefully use this approach to benefit even more patients."
Professor Mahesh Parmar, director of the MRC Clinical Trials Unit where Stampede is based, said the programme was so significant because different treatment options can be investigated quickly and newly developed treatments can be added.
"This is enabling scientists to get results much more quickly than they usually would," he said.
"More data will come out in subsequent years, because of the innovative design of the trial."