Minnesota trial: a yearly stool blood test cuts bowel cancer deaths by a third
Annual faecal occult blood testing followed by colonoscopy for positives reduced colorectal cancer deaths by 33% over 13 years, the first proof that bowel cancer screening saves lives.
The Minnesota Colon Cancer Control Study randomised 46,551 volunteers aged 50-80 to annual guaiac faecal occult blood testing, biennial testing, or no screening. Positive tests led to colonoscopy.
After 13 years, colorectal cancer mortality was 33% lower with annual screening (5.88 vs 8.83 deaths per 1,000); the biennial arm showed a smaller, initially non-significant reduction that became significant with longer follow-up. Thirty-year follow-up (Shaukat 2013) confirmed relative reductions of 32% for annual and 22% for biennial screening.
This trial, with the Nottingham and Funen trials, made stool-based screening the backbone of population bowel cancer programmes, later upgraded to the faecal immunochemical test.
- Colorectal cancer mortality reduced 33% with annual testing at 13 years (5.88 vs 8.83 per 1,000)
- Thirty-year follow-up: relative risk of colorectal cancer death 0.68 (annual) and 0.78 (biennial)
- Rehydrated slides had a high positivity rate (about 10%), so a large share of participants had colonoscopy
- Incidence of colorectal cancer also fell by about 20% at 18 years, attributed to polyp removal
A cheap home stool test, repeated yearly or every two years and followed by colonoscopy when positive, prevents bowel cancer deaths. This is what national bowel screening programmes do today, with FIT replacing the older guaiac test.
- Much of the benefit may have come from the colonoscopies triggered by a high false-positive rate
- Volunteer population; uptake in real programmes is lower
- Guaiac testing has been superseded by more sensitive and specific FIT
- No all-cause mortality benefit was shown, as expected for a single cancer site