Bowel cancer screening in younger groups may do more harm than good

Bowel cancer screening should only be recommended for people at high risk due to their age, family history or other factors, according to new guidelines.

Tests for this cancer have been introduced in most Western countries, usually starting at around the age of 50. Doctors can look at the bowel with a camera on the end of a thin, flexible tube or people can send off a small stool sample so it can be checked for traces of blood.

But a review of the evidence suggests that, in most cases, the benefits are small and uncertain and that screenings aren’t worth possible harms arising from anxiety, false positives and bowel perforations. Screening is worth these possible downsides only in those whose risk of getting bowel cancer in the next 15 years is 3 per cent or more, say Lise Helsingen of Oslo University Hospital in Norway and her colleagues.

The team doesn’t give a firm age cut-off. Instead, it says that doctors should calculate people’s risk using software that uses their age along with other factors such as sex, family history and whether they smoke or drink – but age is the most important element.

“The 3 per cent threshold represents the cumulative risk above which the balance of benefits and harms tilts in favour of screening,” said Philippe Autier at the International Prevention Research Institute in Lyon, France, in an accompanying editorial.

Concerns have also been raised about other cancer screening programmes after their introduction, such as the PSA blood test for prostate tumours and mammograms for breast cancer. The fear is that these programs may do more harm than good by finding tiny tumours that wouldn’t have carried on growing.