Men with prostate cancer could benefit from radical radiotherapy that delivers the treatment in just five days instead of the usual 37.
At the moment, patients must go to hospital from Monday to Friday every week for nearly two months.
But doctors in London are conducting a major trial to deliver a more powerful therapy in five daily sessions.
As well as being more convenient for men, it will save the NHS millions of pounds, and scientists believe it could also reduce side effects.
A trial of 1,800 patients has started at the Royal Marsden Hospital and the Institute of Cancer Research in London. They receive either surgery or a five-day, 37-day or 20-day radiotherapy course. NHS England said in November that the 20-day course should become the standard procedure. Scientists will monitor the men for five years to see whether the five-day course is as effective at defeating prostate cancer as the others.
Around 15,000 men with prostate cancer receive radiotherapy every year – nearly a third of the 47,000 diagnosed in Britain annually.
The treatment is effective, particularly if given at an early stage of the disease, when it permanently eradicates 60 per cent of tumours.
But it can involve long-term side effects, including impotence, bowel problems and even bladder cancer.
The Daily Mail is campaigning to improve prostate cancer treatments and diagnosis, which lag years behind those for other cancers.
The trial involves boosting the radiation power to more than twice the original dose over fewer treatments.
MRI scanning means radiologists can also focus higher radiation on the core of the cancer, rather than irradiating the entire prostate.
Professor David Dearnaley, of the Institute of Cancer Research, said: ‘If you maintain the effectiveness of treatment and make it more convenient, with fewer side-effects, that is really good. We have not proven yet that it is as good, but it’s possible.’