Does bowel cancer screening really help (less mortality)?
For people aged 45 to 75 with average risk, colorectal cancer screening is worthwhile and widely recommended. It demonstrably reduces the likelihood of developing colorectal cancer, although the evidence for short-term mortality reduction is less definitive than previously thought.
Yes, colorectal cancer screening works. Multiple large reviews and international guidelines confirm that screening reduces both the number of new cases and mortality from colorectal cancer1,2,3,4,5,6. The American guideline (USPSTF, 2021) recommends screening for everyone aged 45 to 75 with average risk. Between the ages of 76 and 85 the decision is weighed individually; above 85 screening is no longer recommended.
The strongest direct evidence comes from the NordICC study, the largest randomised trial in this field. People who received an invitation for a one-time colonoscopy had an 18% lower chance of developing colorectal cancer after ten years: the risk fell from 1.20% to 0.98%. It took 455 invitations to prevent one case. An important detail: only 42% of those invited actually went through with the colonoscopy. As a result, the primary analysis underestimates the effect in people who did participate7.
The mortality figures from that same study are more nuanced. After ten years, the difference in colorectal cancer mortality was not statistically significant: 0.28% versus 0.31%. Overall mortality was also virtually identical. This does not mean that screening does not help. Ten years of follow-up may be too short for a slow-growing disease, and the low participation rate blurs the picture. However, these results temper earlier expectations7.
Colonoscopy also carries risks. In the NordICC study, fifteen participants experienced a serious bleed following polyp removal. Perforations or procedure-related deaths did not occur. The risk of complications is small, but it does factor into your personal decision-making7.
The choice of method makes a big difference to uptake. When people can choose from a stool test, colonoscopy, CT scan of the bowel, or sigmoidoscopy, or when an alternative is offered to those who decline the first option, participation rises considerably1,4. The best test is simply the test you actually do. Finally, colorectal cancer is rising in people under 50, which is one reason the recommended starting age has been lowered to 45, although this has not yet been adopted everywhere8.
The claims are based on multiple large reviews, guidelines (USPSTF 2021), and one large European randomised trial (NordICC, PMID 36214590). The general consensus is strong, but the direct evidence for mortality reduction from the only large randomised trial is not yet statistically significant after 10 years of follow-up.