Bowel cancer screening by family history
Risk category and screening plan for someone without symptoms and without a known or suspected genetic syndrome, from the Cancer Council Australia guideline on risk and screening based on family history (version 1.2, May 2026). For surveillance after polypectomy, use thepolyp surveillance calculator.
Enter the age and the family history.
The categories
- Category 1. No affected first or second degree relatives (near average risk), or only one first degree relative diagnosed at 60 or older (above average, but less than twice average).
iFOBT every 2 years from age 45 to 74. - Category 2, at least twice and up to four times average risk. Any of: one first degree relative diagnosed before 60; one first degree relative and one or more second degree relatives at any age; two first degree relatives at any age.
Colonoscopy every 5 years from 10 years younger than the earliest first degree diagnosis, or age 50, whichever is earlier, to age 74. - Category 3, at least four times and up to 20 times average risk. Any of: two first degree relatives and one second degree relative with at least one diagnosed before 50; two first degree relatives and two or more second degree relatives at any age; three or more first degree relatives at any age.
Colonoscopy every 5 years from 10 years younger than the earliest first degree diagnosis, or age 40, whichever is earlier, to age 74.
All categories exclude anyone with a known or suspected genetic syndrome. Low-dose aspirin 100 mg daily should be considered from age 45 to 70 in every category, discussed with the patient.
What changed from the 2017 guideline
- Categories are set by rules rather than the old lookup table, and the age cut-off for a single first degree relative moved from 55 to 60.
- Category 1 screening now starts at 45 rather than 50, in line with the National Bowel Cancer Screening Program.
- Categories 2 and 3 go straight to colonoscopy, and starting 10 years before the earliest first degree diagnosis is back (it had been dropped in 2017).
- Considering low-dose aspirin from 45 to 70 is now part of the advice for all three categories.
- For the genetic syndrome exclusions, the Lynch cancer age cut-off is now 50 rather than 55, and multiple bowel cancers refers to a first degree relative.
Notes
- This is screening for people without symptoms. Anyone with rectal bleeding, iron deficiency, a change in bowel habit or other symptoms needs investigation regardless of the category.
- Count relatives on both sides of the family. Category 2 and 3 criteria can be met using relatives from both sides.
- Reported family history is often incomplete, so it is worth rechecking every few years, and asking the family to confirm diagnoses and ages.
- CT colonography can be offered in category 2 if colonoscopy was incomplete in the previous 3 months, there is a high grade obstruction, or a specialist requests it, and in category 3 if clinically indicated.
- Screening is recommended to age 74. Beyond that, decide case by case.
Reference
Cancer Council Australia Colorectal Cancer Screening Working Party. Clinical practice guidelines for the prevention, early detection and management of colorectal cancer: risk and screening based on family history. September 2023. Sydney: Cancer Council Australia, available from MAGICapp. Version 1.2, published 25 May 2026.Cancer Council clinical guidelines