A major prostate cancer screening trial aimed at finding the best way to detect the disease has been launched in the UK.

The first letters have been sent out from GPs inviting men to join the study, the biggest of its kind in decades.

The £42 million Transform trial is funded by Prostate Cancer UK and the National Institute for Health and Care Research.

Hashim Ahmed, trial chief investigator, said: “Transform is truly game-changing… the start of recruitment today marks a pivotal step towards getting the results men urgently need to make prostate cancer diagnosis safe and more effective so that we can unlock the potential of prostate cancer screening in the UK.”

The trial will recruit men aged 50-74, with a lower age limit of 45 for black men, who have twice the risk of developing and dying from prostate cancer compared with white men.

It won’t be possible to volunteer for the trial, but Prostate Cancer UK is strongly encouraging anyone who receives a letter to take part.

The trial will look at how rapid MRI scans of the prostate could be combined with prostate-specific antigen (PSA) blood tests in order to improve the accuracy of cancer diagnosis.

Currently, men over 50 can request a PSA test, which looks for abnormally high levels of protein in the blood, but this is unreliable, picking up many prostate cancers that would never need treatment, and missing others that do.

The trial will also use spit tests, which extract DNA from saliva, to see if this is more accurate than PSA readings.

Matthew Hobbs, director of research at Prostate Cancer UK, said current diagnostics methods don’t find enough aggressive cancers, and cause too much harm.

“We hear from men who were diagnosed late, whose lives may have been saved if they’d been screened or tested earlier. We also hear from a lot of men who have suffered incontinence or impotence because of treatments they had,” said Mr Hobbs.

“Some of those men didn’t need to have those treatments, and that’s the harm that we need to try to avoid.”

Danny Burkey, 60, from west Yorkshire, is terminally ill with prostate cancer. By the time his condition was diagnosed four years ago, it had already spread to his bones.

The former teacher and father of three told the BBC that if men were offered regular screening from the age of 50, his disease might have been caught when it was still curable.

“I think that a screening programme would be a game changer. If you want men to not be in the position I’m in, and if we want to stop 12,000 men dying early every year, it’s the obvious solution.”

The opening of the trial comes a week before the National Screening Committee (NSC) – an expert body that advises the NHS – is due to announce whether to recommend the introduction of screening for the disease, the most common cancer in men in the UK.

Previously, the NSC had concluded that the harms of screening outweighed the benefits.

Initial results of the Transform trial are due in around two years, after which it will be expanded by up to 300,000 men across the UK.