Bowel cancer screening

How the national program works

Australia runs a free national screening program because bowel cancer, caught early, is one of the most treatable cancers there is, and because it usually causes no symptoms at all until it is advanced. The test looks for blood in the stool that is invisible to the eye.

The current arrangements are straightforward, though one detail catches people out. Screening now starts at 45 and runs to 74, with a test every two years. Kits are posted out automatically from age 50. If you are between 45 and 49, you are eligible but no kit will arrive unless you ask for one, either through the National Cancer Screening Register online or by calling 1800 627 701. The starting age was lowered from 50 to 45 on 1 July 2024, and a good number of people in that band still do not know they can now take part.

The test itself is an immunochemical faecal occult blood test, usually shortened to iFOBT or FIT. It is free, it is done at home, it takes a few minutes, and it involves collecting two small samples from two separate bowel motions and posting them to a laboratory. Results go to you and to the GP you nominate, usually within about two to four weeks.

Participation was 42 per cent in the 2023 to 2024 screening round, and only about a third of people return the very first kit they are sent. A GP who actively hands a kit over and explains it roughly doubles the chance it gets done, which is why it is worth raising at an appointment rather than waiting for the envelope.

Why a home test rather than a camera

It is a fair question. A colonoscopy looks directly at the bowel, so why post out a stool test instead?

The answer is that screening has to be offered to millions of people who are perfectly well, and the value of the program comes from how many people take part rather than from how good any single test is. Repeated every two years across a whole population, the stool test finds cancers early enough to change the outcome, and it does so without putting well people through sedation and a bowel preparation they mostly do not need.

The evidence for this is now long term. In the randomised trials, two-yearly stool testing cut deaths from bowel cancer by about 15 per cent across everyone invited and by about 25 per cent among the people who actually did the test. The protection also lasts: in a British trial followed for 21 years, a single bowel examination in people aged 55 to 64 was still reducing deaths two decades later, by about a quarter overall and by about half in the part of the bowel it can reach. Survival for Australians diagnosed between 50 and 74 has risen from 53 per cent in the late 1980s to 75 per cent in recent years, which screening has contributed to alongside better surgery and better treatment. None of it comes from one test. It comes from doing it again and again.

What a clear result does and does not mean

A clear result means no blood was found in that sample. It does not mean there is no polyp, and it does not mean there is no cancer.

A single stool test picks up roughly three quarters of established cancers but only about one in four of the advanced polyps that would have become one, and bleeding from a polyp or an early cancer comes and goes, so a lesion can easily be present and shed no blood on the day the sample was taken. This is the reason the program is built on repetition. Each round catches some of what the last one missed.

One clear kit at 60 also does not settle the question for the decade before it. The polyps that accumulate through a person's forties and fifties are not undone by a single test late on. Starting on time and repeating on time is what the benefit is made of.

If bowel cancer runs in your family

Family history changes both when screening should start and what form it takes. The national guidelines, updated in 2023, sort people into three broad categories.

• No affected relatives or one first-degree relative diagnosed at 60 or older: the standard screening test every two years from 45.
• One first-degree relative diagnosed before 60, or two first-degree relatives at any age, or one first-degree and one or more second-degree relatives: colonoscopy every five years, starting at 50 or ten years younger than the earliest diagnosis in a first-degree relative, whichever is earlier.
• A stronger family history, such as three or more first-degree relatives, or several relatives with one diagnosed before 50: colonoscopy every five years from 40 or ten years younger than the earliest diagnosis, whichever is earlier.

A first-degree relative means a parent, sibling or child. If several relatives have been affected, anyone was diagnosed young or there is a pattern of bowel, uterine or other related cancers in the family, that is worth discussing properly, because a genetic syndrome changes the approach entirely.

Where a relative was diagnosed under 50, the usual guide for the rest of the family is to start colonoscopy ten years before the age that relative was diagnosed or from 40, whichever comes sooner. This is one of the most commonly missed steps after a young diagnosis in a family.

If your test comes back positive

About one kit in 17 comes back positive, and most of those people do not have cancer. It does mean the bowel needs to be looked at with a colonoscopy, and reasonably soon.

The single most important thing to know is that a positive result is not something to check with a second kit. There is a separate page on what a positive screening test means and what happens next, written for the evening people get the letter.

Where bowel cancer screening is followed up in Sydney

A/Prof Viraj Kariyawasam is a consultant gastroenterologist and hepatologist whose work includes bowel cancer screening and surveillance. Screening questions and positive screening results are seen in Norwest, Rouse Hill, Pennant Hills and Macquarie Park.

The colonoscopy that follows a positive test is performed at Norwest Private Hospital, Macquarie University Hospital and Pennant Hills Day Surgery. A referral from your GP is needed for a consultation.