By Linda Carroll
Rates of early-onset colon cancer are rising in many high-income countries even as rates among older adults hold steady or decline, a new study shows.
The trend toward more colon cancer in younger adults began in the mid-1990s, according to the report published in Gut.
The new findings mean that "if you have symptoms consistent with colorectal cancer, you should follow up with a physician no matter what your age is," said coauthor Rebecca Siegel, scientific director of surveillance research at The American Cancer Society. "The most common symptoms in young people, based on our surveys, are the same as in older patients: constipation, blood in the stool or rectal bleeding, bloating, diarrhea, more narrow stool than usual, gas, pain, cramping."
A day or two of these kinds of symptoms probably doesn't indicate colon cancer, Siegel said. "But if you have these symptoms for two to three weeks, then get it checked out," she added.
Siegel and colleagues studied global data looking for clues as to why early onset-colon cancer appeared to be rising in the U.S. "And there is a common thread," she said. "So now we can point to some clues."
This "only seems to be happening in high-income countries and it started around the mid-1990s when something changed in terms of exposure," Siegel said. "It's probably a combination of things that started to change the risk for the disease."
One likely candidate is dietary changes, Siegel said. "The food supply changed immensely in the last half of the 20th century," she added. "While it's almost like looking for a needle in a hay stack, there have been at least a couple of studies looking at sugar-sweetened beverages that found even moderate consumption increases risk. And it's not just sugar-sweetened beverages, but also high fructose corn syrup with a positive association. High glycemic load carbohydrates can create a highly inflammatory environment in the gut."
From 2008 through 2012, among the 42 countries with high-quality cancer registry data, colon cancer rates among people ages 20 to 49 were lowest in India (3.5 per 100,000), Uganda (3.8 per 100,000) and Chile (3.8 per 100,000) and highest in Korea (12.9 per 100,000), Australia (11.2 per 100,000), the U.S. (10.0 per 100,000), and Slovakia (10.0 per 100,000).
Other countries that saw an increase in early onset cancer were Canada, Denmark, Germany, New Zealand, Slovenia, Sweden and the UK.
The steepest increases in younger adults were in New Zealand, where the annual average percent change was 4%, and in Korea, where it was 4.2%.
While rates of early-onset disease were going up, onset rates in older people were declining in New Zealand, Australia, Canada and the U.S.
Although this isn't the first study to show that early onset rates are on the rise, "it's very alarming," said Dr. Edward Chu, a cancer specialist and deputy director of the UPMC Hillman Cancer Center at the University of Pittsburgh School of Medicine. "We're seeing a pretty significant increased incidence among those aged 40 to 49. They also tend to have much more aggressive disease and tend not to do well even with aggressive treatments."
While doctors might historically have attributed "abnormal symptoms GI symptoms in younger patients to benign causes, you can no longer blow these symptoms off," Chu said. "You have to be vigilant and more aggressive in trying to determine the causes of those symptoms."
Unfortunately, Chu said, colon cancer can be "a silent disease."
So it makes sense for people to focus on prevention, which amounts simply to living a healthy lifestyle, Chu said. "Cut down on red meat, increase fruit, vegetable and fiber consumption," he added. "Try to be physically active, don't smoke, and lose weight if you're overweight."