New diagnoses of colon and rectal cancers are on the rise among young adults while the numbers are falling in people who are older, according to a new study.
Cases to double by 2030
If the trends continue, by 2030 the number of colon and rectal cancer cases will roughly double among people between the ages of 20 and 34 years old and grow by 28 percent to 46 percent in people ages 35 to 49 years, researchers found.
"You have to recognise that the incidence rate is increasing in young patients and you have to take their complaints seriously," Dr. Christina Bailey told Reuters Health.
Read: More African Americans die from colon cancer
Bailey, the study's lead author from the University of Texas MD Anderson Cancer Centre in Houston, said it's unclear why those cancers are increasing among young people. But doctors cannot assume that a younger person isn't likely to have colorectal cancer.
If physicians evaluate younger people who have symptoms commonly tied to colon and rectal cancers, hopefully those patients can get an earlier diagnosis to improve outcomes, Baily said.
50 310 estimated deaths
The National Cancer Institute estimates there will be about 96 830 new colon cancers and 40 000 new rectal cancers diagnosed in the U.S. in 2014. There will also be about 50 310 deaths from those types of cancer.
According to the American Cancer Society, about one in 20 people will be diagnosed with colon or rectal cancer during their lifetime.
Currently, the government-backed U.S. Preventative Services Task Force recommends that people ages 50 to 75 get screened for colon cancer using faecal occult blood testing, sigmoidoscopy or colonoscopy.
The suggested interval between screenings depends on the method – from faecal tests every year to colonoscopy every ten years.
The researchers write in JAMA Surgery that thanks to increased screenings, the number of new colon and rectal cancers diagnosed has been decreasing, because doctors can remove suspicious growths before they turn into cancer.
But there have been other reports that the number of new cases being diagnosed among younger people is growing.
"We've been seeing more young patients in our clinic for workups for colorectal cancers," Bailey said.
The researchers used a U.S. database of cancer cases from 1975 to 2010 to determine the incidence of colon and rectal cancers among different age groups.
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Overall, the incidence of those cancers for all age groups fell by about 1 percent during that period. The decrease was confined to those 50 years and older, however. There were increases for people between 20 and 49 years.
The researchers also found an increasing number of advanced cancers were being diagnosed among younger people.
Still, people between ages 20 and 49 years made up only a small portion of the total colon and rectal cancers. Those aged 20 to 34 made up 1 percent of all cases and those aged 35 to 49 made up about 7 percent of all cases.
Using a computer model, the researchers predict that the number of new colon cancers among people ages 20 to 34 will increase by 90 percent, and the number of new rectal cancers will increase by about 124 percent by 2030.
They also project smaller increases in colon and rectal cancer incidence among people between the ages of 35 and 49 years.
"It poses the question, what is the fact that's leading to this increase?" said Dr. Kiran Turaga from the Medical College of Wisconsin in Milwaukee.
Reasons could be lifestyle related
The researchers can't say why more colon and rectal cancers are being diagnosed among younger people, but it could be attributed to less healthy lifestyles; for example, being obese, not exercising and having a poor diet.
Bailey said doctors and patients may not consider colon cancer at first, which would also explain the greater number of advanced cancers among young people.
They can't rule out other influences that could lead to increased rates of cancer, however.
"We don't want to send the message that people in their 30s should be running out and getting a colonoscopy," Dr. Donald David said.
David, who was not involved with the new study, is chief of gastroenterology at City of Hope, a comprehensive cancer centre, in Duarte, California.
"It's a very individual sort of thing," David said. "There is a national prescription for most people, but there are individual circumstances that only you and your doctors are going to be able to figure out."
Turaga, who wrote an editorial accompanying the new study, said people should still watch for symptoms. Those include bloody stools, unexplained weight loss and changes in bowel movements.
Read: Rectal cancer
"The vast majority of people don't have to worry about it," he said. "They need vigilance like (with) breast cancer where there are so many people looking for lumps and those sorts of things."
He also said it may be a wake-up call for people to shift to more healthy diets.
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Image: Colon cancer treatment from Shutterstock.