Maybe it was already there when he was at Disney World. Ryan O’Grady, Ph.D., stated that he could not rule out the possibility while sitting in his office on a late-winter morning wearing jeans and a hooded sweatshirt that featured a teddy bear dressed in a business suit on the front. “I don’t know. It’s hard to say for sure, but I’m thinking about it,” Dr. O’Grady, a mathematics professor at a small liberal arts college in Pittsburgh’s northern suburbs.
It was February 2023, on that family trip with his wife and two young daughters, when Dr. O’Grady started out with some uncomfortable digestive issues. He didn’t see any reason to be concerned at the time, 43 years old and generally healthy. But as the year went on, the problems started occurring more regularly. Finally, with the holiday season approaching, his gastrointestinal difficulties became more frequent and more severe. With some spirited encouragement from his wife, Dr. O’Grady went to the emergency room. That led to a doctor’s appointment and, thanks to an opportune cancellation, a quickly scheduled colonoscopy.
Finally, two days after Christmas 2024, the call came from his doctor: colorectal cancer.
“We were supposed to go to Columbus for a late Christmas with my brother and his family,” Dr. O’Grady stated After some hesitation, they did go. To keep his mind from going down depressing rabbit holes, he spent a lot of time at his brother’s house working. “My wife was calling to make a variety of doctor’s appointments for me,” Several decades ago, aside from people with certain genetic predispositions, a diagnosis of colorectal cancer in somebody under age 50 was unusual. But that’s no longer the case.
Y. Nancy You, M.D., who specializes in treating colorectal cancer at the University of Texas MD Anderson Cancer Center, said that when she was finishing her medical fellowship in 2009, the average age of people in the United States diagnosed with the disease was 72.
“Now it’s 67,” she said.
And it’s not just colorectal cancer that’s being diagnosed more frequently in people under age 50. Breast, uterine, and kidney cancers, among other common cancers, are also on the rise. The increase has been most stark among people in the 20–29 age range.
The trend has left many researchers perplexed and alarmed. And although there are some hints about why this might be happening, there are no definitive answers yet, said Dr. You, as the program director for MD Anderson’s Young-Onset Colorectal Cancer. “I don’t think there’s going to be a single ‘smoking gun,’” she continued. “It’s the million-dollar question everybody [is asking]. But it’s a long-term response.” A harbinger of a larger problem
The uptick in early-onset cancers started to garner public attention in 2020 when the actor Chadwick Boseman, the star of the Black Panther film series and other hit movies, died from colorectal cancer at the age of 43.
On the big screen, Boseman was handsome, muscled, and by all appearances the epitome of well-being. He was the last person many people expected to be diagnosed with, let alone die from, cancer.
But relative youth is no longer the forcefield against colorectal cancer that it used to be. Early-onset colorectal cancer “is becoming the leading cause of cancer deaths among young adults in the United States,” said Yin Cao, MS.c., of the Washington University Siteman Cancer Center in St. Louis.
Dr. Cao is leading a first-of-its kind research program called PROSPECT that’s investigating the causes of early-onset colorectal cancerExit Disclaimer. Funded by NCI, Cancer Research UK, Bowelbabe Fund, and Institut National du Cancer through the Cancer Grand Challenges program, PROSPECT is international in scope, and with good reason, she explained during a December 2024 NCI advisory board meeting.
One recent study, for example, found that nearly 10% of new colorectal cancers around the world are in people under the age of 50. In addition, early-onset colorectal cancer rates have increased in 27 of the 50 countries included in an analysis by researchers from the American Cancer Society (ACS). More cancers are being diagnosed in older people as well
Recent studies have brought the scope of the early-onset cancer phenomenon into tighter focus. Their results confirm that the trend extends beyond colorectal cancer.
An NCI-led study published in May provided one of the most comprehensive analyses of trends in the United States. Looking at data captured in two large databases, they found that rates of 14 cancer types increased in at least one age group among people under 50Exit Disclaimer (i.e., 15–29, 30–39, and 40–49 years old) between 2010 and 2019.
But rates of new diagnoses for nine of these same cancers also increased in people over age 50 in at least one 10-year age group, explained the study’s lead investigator, Meredith Shiels, Ph.D., of NCI’s Division of Cancer Epidemiology and Genetics.
The ACS study on early-onset colorectal cancer showed that the same thing is happening globally, with the rise in colorectal cancer diagnoses “frequently occurring alongside the increase in older adults.”
As these findings make clear, Dr. Shiels said, future research can’t ignore what’s happening in older people.
“We can learn something … by looking across all age groups,” she said.
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What’s behind the rise in early-onset cancers?
The cause of the trend toward cancer with early onset is unclear. However, a number of studies have identified the same potential culprits. More than a few studies have singled out obesity and heavy consumption of alcohol as likely key contributorsExit Disclaimer. Others have suggested that environmental factors, like an overabundance of microplastics in the bodies of younger people, might be at play.
Much of the available evidence places the blame on another potential culprit: disruptions in the composition of bacteria in the gut and elsewhere in the body, known as the microbiome. One recent study also implicated bacteria. But, rather than a harmful mix of these organisms, it suggested that a DNA-damaging toxin produced by certain strains of the bacterium E. coli may be a key driver.
There are a lot of potential contributing causes, said Ulrike Peters, Ph.D., of the Fred Hutch Cancer Center, during a session on early-onset cancers at the annual meeting of the American Association of Cancer Research (AACR) in April.
But, Dr. Peters continued, “For many of these [factors], there’s no strong epidemiological evidence that they’re [individually] linked to early-onset cancers.”
Some researchers believe that with colorectal and some other cancers, what’s being seen is a so-called birth cohort effect.
In the case of colorectal cancer, as an example, for many decades the disease was predominantly diagnosed in people in their 60s and 70s. However, starting with people born in the 1950s and becoming more pronounced for those born in the decades that followed, exposure to changing environmental, lifestyle, and other risk factors may have accelerated the time it takes for colorectal cancer to develop in individuals.
In other words, Dr. You said, a “whole package” of common factors has created a new biologic window of opportunity for cancer to take hold in younger populations.
Are early-onset cancers biologically different?
A critical question for researchers has been whether early-onset cancers are biologically different in some key ways from cancers diagnosed in older people. Such information, experts agree, could help single out the key contributors to the phenomenon. In the more immediate term, it could help inform choices about the best treatments and patterns of care for younger people.
Overall, the findings on potential genetic or other biological differences in sporadic early-onset cancers—that is, those not linked to inherited cancer-related genetic change—haven’t provided anything definitive, said Rihab Yassin, Ph.D., of NCI’s Division of Cancer Biology.