Bowel Cancer in under 45s

Most bowel cancer cases are diagnosed in people aged 50 and over, but the picture is changing.

Today, one in 8 Australians diagnosed with bowel cancer are under 50.⁴

The risk of being diagnosed before age 40 has doubled since 2000⁵, and people born in 1990 are up to three times more likely to develop bowel cancer than those born in 1950.⁶

“Australia has the highest rates of early-onset bowel cancer (people diagnosed under 50) in the world,” says Medical Director at Bowel Cancer Australia, Associate Professor, Graham Newstead.

“Rising rates of early-onset bowel cancer is a global phenomenon, but we don’t why it’s happening,” he says. “Most cases are sporadic, or don’t have a known hereditary component.

“Underlying causes are largely unknown; however, it is highly likely the incidence in young people will prove to be a combination of environmental factors, such as foods we eat, plus the effect of these factors on our genetic makeup.”

What we do know the single biggest risk factor for bowel cancer is increasing age.

“Around 87.5% of bowel cancer cases are diagnosed in people over age 50⁷,” says Graham.

Bowel cancer is also known as colorectal, colon, or rectal cancer. It can affect any part of the colon or rectum. The colon and rectum are parts of the large intestine.

It develops from the inner lining of the bowel and is usually preceded by growths called polyps, which can turn into cancer if undetected.

Early symptoms of bowel cancer can include:

Blood in your poo

Obvious change in your bowel habit

Weight loss you can’t explain

Extreme tiredness for no reason

Lump or swelling in your abdomen

“Around 30% of all bowel cancer cases diagnosed are due to a hereditary contribution, family history, or a combination of both⁸,” says Graham.

“The other 70% of people have no family history of the disease and no hereditary contribution.”

“Diet and lifestyle choices, as well as screening and surveillance, can influence your bowel cancer risk.”

“Risk factors such as obesity, lifestyle and diet are associated with an increased risk of bowel cancer irrespective of age.”

“Researchers are investigating antibiotic use, accelerated aging, microplastics, and ultra-processed foods as possible risk factors for early-onset bowel cancer.”

“Bowel cancer screening is for people who do not already have bowel cancer, symptoms of bowel cancer, or any reason to have a high risk of bowel cancer,” says Graham.

Different screenings are appropriate at different ages:

People aged 40 to 44

“Medical guidelines state health care professionals could consider offering screening (an immunochemical faecal occult blood test) every 2 years to people aged 40 to 44, who request screening following a discussion about the benefits and potential harms”.

People aged 45 to 74

“For people at average risk of bowel cancer and without symptoms, Australian medical guidelines recommend screening using a faecal immunochemical test (FIT) every 2 years between ages 45 to 74.”

People aged 75 to 85

“Medical guidelines state health care professionals could consider offering an immunochemical faecal occult blood test to fit, well and healthy people aged 75-85 years, who request screening after a discussion about the benefits and potential harms.”

“Any symptoms of bowel cancer or positive screening test require investigation,” says Graham. “This is done via a colonoscopy. A colonoscopy is a quick and generally painless procedure that allows for the full examination of the entire inner lining of your bowel.”

“If you experience any symptoms for 2 weeks or more, see your GP and have them investigated,” says Graham.

“Blood in your poo or rectal bleeding is not normal and should never be ignored."

Bowel cancer is highly treatable when caught early, with more than 9 in 10 people surviving at least five years when it is diagnosed at an early stage.³