Since the 1990s, more patients under 50 are learning they have colorectal cancer, said Reinier Meester, PhD, a postdoctoral scholar in gastroenterology and hepatology. But it's not clear whether the increase in the number of diagnoses stems from people developing cancer at younger ages or whether physicians are simply finding the disease earlier.
"There's been a debate about underlying causes," Meester said.
Meester and his colleagues set out to figure out what was going on. They reasoned that if the cancer is being found at earlier stages, that indicates that screening may be responsible for the uptick in diagnoses. But if the cancer is being discovered at similar or later stages, that suggests the cancer is developing in younger people.
The researchers looked at 29,532 cases of colorectal cancer diagnosed between 1975 and 2015 and occurring in patients ages 40 to 49. They found that the cancer is currently being discovered at later stages than it was 25 years ago -- meaning the risk of developing colon cancer at a younger age is likely increasing.
Their research appears in the Journal of the American Medical Association.
Now that we know there's a greater risk of colorectal cancer in people of younger ages, Meester said, researchers can turn their attention to prevention and detection.
Using colonoscopies to screen for cancer can not only detect cancer early, but can also prevent it from developing. For the over-55 crowd, colorectal cancer rates have been decreasing, likely because many over 50 undergo colonoscopies, during which physicians remove precancerous polyps.
As to why there is an increase in risk in those under 50, Meester said, "Obesity and an unhealthy diet may play a role, but it's mostly still unknown."
Photo of Reinier Meester by Mandy Erickson