Starting colorectal cancer screening at ages 45–50: use fecal immunochemical tests or colonoscopies

19. Starting colorectal cancer screening at ages 45–50: use fecal immunochemical tests or colonoscopies

Cost: Fecal tests cost just a few dozen yuan and can be done every 1–2 years. Colonoscopies cost several hundred to over a thousand yuan; those with negative results only need one every 10 years. Preparing for a colonoscopy requires setting aside a full day for bowel cleansing.

In plain terms: Getting a low-cost fecal occult blood test every year or two lowers the chance of dying from colorectal cancer by roughly 16%. For people who’ve had at least one round of screening, this risk drops by about 25%. In the group invited to undergo a colonoscopy, the likelihood of developing colorectal cancer over the next decade fell from 1.20% to 0.98%.

Benefit: Cochrane pooled data from multiple studies showing that individuals undergoing fecal occult blood screening have a roughly 16% lower risk of dying from colorectal cancer. The original RR was 0.84, with a 95% CI ranging from 0.78 to 0.90. For those who’ve had at least one screening round, this risk reduction reaches 25% (RR 0.75). The NordICC randomized trial likewise found that among participants invited to get a colonoscopy, colorectal cancer incidence dropped from 1.20% to 0.98% over 10 years; its RR was 0.82, with a 95% CI of 0.70–0.93.

Evidence grade: A

Sources: Hewitson P et al. (2007). Screening for colorectal cancer using the faecal occult blood test, Hemoccult. Cochrane Database of Systematic Reviews. <https://doi.org/10.1002/14651858.CD001216.pub2>; Bretthauer M et al. (2022). Effect of Colonoscopy Screening on Risks of Colorectal Cancer and Related Death. New England Journal of Medicine. <https://doi.org/10.1056/NEJMoa2208375>

Notes: This topic remains debated. The NordICC trial tracked participants based on whether they were invited to get a colonoscopy; the difference in colorectal cancer mortality between groups was 0.28% versus 0.31% (RR 0.90, 95% CI 0.64–1.16), a gap well within statistical margins of error. This suggests earlier estimates of colonoscopy’s mortality benefits may have been overstated, while evidence for fecal tests’ impact on mortality is more robust. Most national guidelines recommend starting screening at ages 45–50; those with a family history of colorectal cancer should begin even earlier.