Bowel Cancer Screening

Bowel cancer rarely appears suddenly. It usually develops over many years from small polyps that grow silently in the lining of the large bowel. By the time symptoms appear, the disease may be advanced.

Screening aims to detect these changes before they cause symptoms. Bowel cancer is generally more treatable when it is identified at an earlier stage. Where colonoscopy identifies polyps, they can often be removed during the procedure, which may reduce future bowel cancer risk.

Screening recommendations depend on individual risk. Most adults in the general population fall into the average-risk category, while a smaller group has higher risk because of family history, previous polyps or another medical condition.

Average risk: a home FIT test every two years from age 45 to 74 through the National Bowel Cancer Screening Program. Kits are mailed automatically from age 50, and people aged 45 to 49 can request their first kit.

Family history of bowel cancer or advanced polyps: screening recommendations vary according to the number of relatives affected, how closely they are related to you and their ages at diagnosis. Some people with a significant family history may need to begin screening earlier or have colonoscopy rather than routine bowel screening. Your GP or specialist will confirm which pathway applies to you.

Suspected hereditary cancer syndromes (such as Lynch syndrome or familial adenomatous polyposis): specific screening programs apply, and genetic assessment may be recommended.

Personal history of polyps or bowel cancer: surveillance colonoscopy at intervals guided by previous findings and your individual risk.

Inflammatory bowel disease affecting the colon: some people require surveillance colonoscopy after several years of disease. Timing depends on the extent and duration of inflammation and other risk factors, including primary sclerosing cholangitis and family history. Your gastroenterologist or colorectal specialist will advise when surveillance should begin.

The faecal immunochemical test (FIT) is a simple home test that detects tiny amounts of blood in the stool that cannot be seen. People aged 50 to 74 are mailed a free kit every two years by the National Bowel Cancer Screening Program. People aged 45 to 49 can request their first kit online or by calling 1800 627 701.

The test detects blood, not its source. Bleeding may come from a polyp or cancer, but also from haemorrhoids or other harmless causes. A positive result does not mean cancer. It means colonoscopy is needed to find the cause.

Colonoscopy is the most accurate test of the large bowel. It allows direct visualisation of the bowel lining and treatment of polyps in the same procedure. It is the recommended screening test for people with a significant family history, and the recommended follow-up to any positive FIT result.

Surveillance colonoscopy is used to monitor patients who have previously had polyps or bowel cancer. The interval is individualised based on the number, size and pathology of any polyps found.

Screening is intended for people without symptoms. Anyone with the following symptoms should be reviewed by a GP and considered for colonoscopy, regardless of screening history or a previous normal FIT test.

• Rectal bleeding or blood mixed with stool.
• Persistent change in bowel habit (looser, more frequent or constipated).
• Unexplained abdominal pain or bloating.
• Unintended weight loss.
• Iron deficiency anaemia of uncertain cause.
• A feeling of incomplete emptying after bowel motions.

A small proportion of patients carry an inherited genetic syndrome such as Lynch syndrome or familial adenomatous polyposis (FAP). These conditions require specific surveillance programs and may warrant referral for genetic assessment.

If your FIT is negative, repeat it every two years. If you have a colonoscopy and no polyps are found, the Program will usually advise you to skip your next test and resume screening four years after the colonoscopy. If polyps are removed, your specialist will confirm when your next colonoscopy is due once the pathology results are available. See Colonoscopy and Polyp Removal for how intervals are decided.