Bad news on bowel cancer for the young

While colorectal cancers rates are heading down among older people, they are heading up among the young. Dyani Lewis reports.

Rates for colorectal cancers are on the rise for Gen X

Bowel cancer rates are falling, but not for everyone. Young and middle-aged adults are bucking the trend, with numbers on the rise, according to US research.

A study led by Rebecca Siegel of the American Cancer Society, based in Atlanta, Georgia, looked at nearly half a million cases of colon and rectal cancer in US populations between 1974 and 2013. Colon cancer rates have been steadily falling for people over the age of 55 since the mid-1980s. The same trend kicked in even earlier for rectal cancer.

That’s not the case for younger adults. Rates have either plateaued or are trending upwards, with the greatest increase in the youngest age group analysed – those in the 20s.

For colon cancer, the rate of diagnosis in 20-somethings sat at around 0.5 cases per 100,000 people in the mid-80s. By 2013, that rate had doubled, a change of more than 2% per year over that time.

The increase was even steeper for rectal cancer – more than 3% per year since 1974.The rise could have alarming implications for what to expect as Gen Xers and Millennials age, according to Siegel. "Trends in young people are a bellwether for the future disease burden," she says.

The worrying trend isn’t isolated to the US, according to Mark Jenkins from the University of Melbourne, who was not involved in the study. Jenkins’ own unpublished data reveals a similar up-tick in colorectal cancer cases in young Australians, though he notes that cases are still rare.

"Even though the risks might be increasing, the risks are minuscule," he says. “A 50-year old is 40 or 50 times more likely to get colorectal cancer than a 20 year old.”

The next step will be for researchers to pin down the likely culprits. Lifestyle factors are already in their sights.

“Western countries have the highest rates of colorectal cancer in the world, and the thinking is it's related to obesity and diet,” says Jenkins.

Excess body weight, diets rich in processed meat and alcohol, and low in fibre, as well as sedentary lifestyle and smoking have all been linked to an increased risk of developing colorectal cancer.

In Australia, older adults benefit from established screening programs that detect cancers and their precursors early. The National Bowel Cancer Screening Program will see all Australians aged 50-74 screened every 1-2 years by 2020.

Screening is also recommended for those over 50 in the US, but the authors suggest a younger age should be considered.

Jenkins disagrees. “The risks of screening and the costs far outweigh the benefits that you would get," he says.

The study is published in the Journal of the National Cancer Institute.

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