Researchers say that men with slow-growing prostate cancer shouldn’t be given radiotherapy; the treatment increases the risk of bowel cancer by 68 per cent, rectal cancer by 62 per cent and bladder cancer by 39 per cent.

Radiotherapy is routinely given to men who have recently been diagnosed with prostate cancer, and often in the early stages, and is often preferred to surgery, which can leave the patient impotent or incontinent.

It appears that radiotherapy causes mutations in cells throughout the body, say researchers from the University of Toronto, who reanalysed 21 previously-published studies.

They compared the rate of secondary cancers in men who had radiotherapy and those who didn’t. Most of the cancers appeared after 10 years, and so their findings are especially significant in men whose prostate cancer is slow growing, and who are likely to live with the disease for more than 10 years.