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UCI Health expert sees colorectal cancer on the rise in younger adults

March 27, 2023
Gastroenterologist Dr. William E. Karnes leads the high-risk colorectal cancer screening program for the UCI Health Digestive Health Institute.
UCI Health gastroenterologist Dr. William E. Karnes is "shocked" by the frequency of colorectal cancers he is finding in younger adults. Photo by Steve Zylius/UCI 

IN THE NEWS: Colorectal cancer, which has been on the rise in ever younger adults, is projected to become the leading cause of U.S. cancer-related deaths by 2040 among people between ages 20 to 49, according to a recent study.

A parallel spike in childhood obesity may be linked, said Dr. William E. Karnes, a gastroenterologist and director of high-risk colorectal cancer services at the UCI Health Digestive Health Institute.

“The rise in young-onset colorectal cancer correlates with a doubling of the prevalence of childhood obesity over the last 30 years, now affecting 20% of those under age 20,” said Karnes, who recently spoke with CNN Health about the issue.

“However, other factors may exist,” he said, adding that he has been "shocked" by the increasing frequency of colorectal cancer in his younger patients.

Genetics also plays a role. Lynch syndrome is the most common cause of hereditary cancers, resulting in about 4,200 U.S. colorectal cancer cases each year. People with Lynch syndrome are more likely to get colorectal, uterine, ovarian and other cancers before turning 50, Karnes said.

However, "it is unlikely” that Lynch syndrome accounts for all the increased cases of colorectal cancer in younger adults, he added. 

Regardless of the causes, Karnes says early detection saves lives. The American Cancer Society now recommends beginning regular colorectal cancer screening at age 45. 

“It’s important for people to know that regular physical exams and cancer screenings improve their odds for preventing cancer altogether or catching it in its earliest stages,” he said

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