Colon Cancer Mysteriously on the Rise Among Younger Americans, and Doctors Not Sure Why

An undated U.S. National Library of Medicine X-Ray photo shows a sigmoid adenocarcinoma, a type of colorectal cancer. US National Library of Medicine

A larger percentage of younger people are being diagnosed with colorectal cancer, according to a new report released Wednesday, and researchers say they don’t know why.

The American Cancer Society said Wednesday that about 1 in 5 new colon and rectal cancers are among those in their mid-50s and younger. The proportion of these types of cancers among adults younger than 55 increased from 11 percent in 1995 to 20 percent in 2019, it found.

Researchers noted that there appears to be a broader shift to more diagnoses of advanced stages of cancer.

The trend, they wrote, is “shifting to younger individuals as cohorts born in the last one half of the 20th century who have elevated risk age; one in five new cases now occur in individuals in their early 50s or younger,” according to a report published in the American Cancer Society Journals.

“Second, there is an overall shift to later stage disease, with more individuals now diagnosed at an advanced stage than in the mid-1990s before widespread screening,” the paper said. “Finally, there is a shift from right-sided to left-sided tumors, despite higher efficacy for preventing the latter through screening, likely reflecting changes in underlying disease risk of unknown etiology.”

In an interview with CNN, the American Cancer Society’s Dr. William Dahut said that “it’s not rare for us now to hear about a young person with advanced colorectal cancer,” noting, “It used to be something we never heard or saw this, but it is a high percentage now of colorectal cancers under the age of 55.”

Dahut pointed to people’s diets and other environmental factors. He did not offer specific details.

“We’re not trying to blame anybody for their cancer diagnosis,” Dahut told the outlet. “But when you see something occurring in a short period of time, it’s more likely something external to the patient that’s driving that, and it’s hard not to at least think—when you have something like colorectal cancer—that something diet-related is not impossible.”

A woman shops for groceries at a supermarket in Monterey Park, Calif., on Oct. 19, 2022. Frederic J. Brown/AFP via Getty Images

Arif Kamal, the chief patient officer for the American Cancer Society, said that the rise in obesity among younger Americans should be tied to colorectal cancer. He said that people in their 40s and 50s, for example, are eating more processed foods and less fiber than previous generations.

“As obesity rates continue to rise in the United States, we have to identify colorectal cancer as an obesity-related cancer the same way we did when we started to think about lung cancer being a smoking-related cancer,” Kamal told the Washington Post of the latest findings. “It will help people see that one thing leads to another.”

However, another doctor not involved in the research said that the rise in colorectal cancer rates might be tied to environmental factors, not diets.

“I see so many young patients who live really healthy lifestyles that get diagnosed with metastatic colon cancer,” Dr. Kimmie Ng, director of the Young-Onset Colorectal Cancer Center at Dana-Farber Cancer Institute in Boston, told the Wall Street Journal. “There are other environmental exposures that need to be looked at.”

Colorectal cancer is the third most common cause of cancer fatalities among Americans, according to the American Cancer Society. It noted, however, that the death rate from colorectal cancer has dropped in recent decades.

Alaska Natives, Native Americans, and black people have higher rates of colorectal cancer rates and deaths among other groups, the researchers said. Also, men have higher case rates than women, they found.

There are also higher mortality and case rates in the Appalachia region as well as parts of the Midwest and South, the organization said.

One of the conclusions in Wednesday’s report stated that more younger Americans should get screened for colorectal cancer earlier.

“We know rates are increasing in young people, but it’s alarming to see how rapidly the whole patient population is shifting younger, despite shrinking numbers in the overall population,” Rebecca Siegel, senior scientific director of surveillance research at the American Cancer Society, said in a news release. “The trend toward more advanced disease in people of all ages is also surprising and should motivate everyone 45 and older to get screened.”