Colorectal cancer in children aged 10 to 14 rose sixfold from 1999 to 2020, study finds

Colorectal cancer remains the second leading cause of cancer deaths in the United States. Its profile is shifting.

Rates have fallen for more than a decade in adults over 65. Among the young, they are climbing.

The numbers

One study found colorectal cancer incidence rose sixfold among children aged 10 to 14 between 1999 and 2020. Among teens 15 to 19, the disease more than quadrupled. Among adults 20 to 24, it nearly doubled.

A second study found incidence was relatively stable from 1999 to 2012. After that, cases among 10-to-14-year-olds began rising at an estimated 70.54% a year from 2012 to 2015. Compounded, that is a nearly 400% increase over three years.

The starting point is tiny. Only a few hundred cases a year are diagnosed in people under 21 in the U.S.

The disease is overwhelmingly one of older age. A 2026 study in the American Cancer Society's flagship journal found 55% of all colorectal cancers are diagnosed in people over 65. Only 16% occur in people 49 or younger.

The youth increase also fits a wider pattern. Colon and rectal cancer rates have been rising overall in people under 50.

Aggressive when it appears

The rise is only part of the concern. When colorectal cancer shows up in the young, research indicates most cases are advanced, at Stage 3 or 4. Another paper suggests these patients are more likely to see the cancer return after treatment.

Dr. Erica Arnold, a pediatric surgery research fellow at Nationwide Children's Hospital in Columbus, Ohio, presented new work this month at the American Academy of Pediatrics annual meeting. Her team analyzed 84 patients aged 21 or younger.

"We do feel like it is a bit of a distinct disease than what we're seeing in older adults," Arnold said.

In that research, about 12 weeks passed between a patient's first symptoms and diagnosis. Despite treatment, the cancer returned in 37% of patients. By the end of the study, 45% had died of the disease.

Delay or different biology?

There are two competing explanations for the poor outcomes, and they are not mutually exclusive.

Dr. Christopher Lieu, a professor of medical oncology at the University of Colorado Anschutz and a medical adviser to the nonprofit Colorectal Cancer Alliance, said some of the poor outcomes may stem from delayed diagnosis. Young patients rarely get screened and are rarely suspected of having the disease.

But Lieu said that is not the whole picture. "If you want my honest opinion, it does suggest that these cancers are developing differently," he said.

What drives it is unknown

No one has identified a cause. Researchers suspect environmental factors, including ultraprocessed foods, lack of exercise and obesity.

Most of the research into causes has focused on the gut microbiome, the community of bacteria and other microbes in the intestines, Lieu said. The working theory is that disruptions in the microbiome spur long-term inflammation, which may trigger the DNA mutations that lead to cancer. Researchers are also asking whether antibiotics disturb the balance of the gastrointestinal system.

Lieu cautioned against a simple answer. "It's going to be extraordinarily more complex than that," he said, adding that there likely is not one reason young people's microbiomes are being disrupted.

Why older adults are different

The split between age groups has a partial explanation. People over 50 receive routine colonoscopies in which precancerous polyps are removed. That likely accounts for much of the decline in diagnoses among older adults.

Children and teens do not get that kind of screening. For them, diagnosis depends on symptoms being recognized and acted on.

The unresolved question is whether earlier recognition can change those outcomes. Arnold's 12-week gap between symptoms and diagnosis, set against Lieu's view that the biology itself differs, leaves open how much of the 45% death rate in her study earlier detection could have prevented.

Research into the microbiome and other suspected causes is continuing.