In such situations, men should be given detailed information about the risks and benefits of treatments which can cause incontinence and erectile dysfunction, it says.
Every year, around 100,000 men with suspected prostate cancer undergo biopsies in an attempt to detect the disease.
Now the National Institute for Health and Care Excellence (Nice) has said MRI scans should be offered as the “first line investigation” for all those with suspected localised prostate cancer.
Research suggests that as a result, around 28 per cent of such cases could be spared gruelling and invasive biopsies.
For the remainder, the combination of MRI with biopsy was far more likely to lead to detection of the most invasive cancers.
Research in the Lancet last year found that among those with cancer, the new technique picked up 93 per cent of aggressive cases, compared with 48 per cent caught by traditional biopsy.
Prostate cancer is the most common cancer in men, with 47,000 cases annually, leading to 11,000 deaths.
But it is notoriously difficult to diagnose, as many possible symptoms – such as needing to urinate more frequently at night – become more common among men with age.
GPs use examinations and blood tests which check prostate-specific antigens to check for heightened risk of disease, but these too can be unreliable indicators.
And some cases of prostate disease grow very slowly, meaning many men end up being treated for cancer which would never have killed them.