Colon cancer is officially the deadliest cancer for people under 50 in the US — a shift that happened more rapidly than cancer researchers expected.
As Business Insider reports, new data shows that in 2023, colon cancer eclipsed breast cancer, which had been the leading cause of cancer death in young adults for over a decade. Before that, lung cancer was the big killer. American Cancer Society epidemiologist Rebecca Siegel, senior author of the new report published in JAMA on January 22, told Business Insider she was “very surprised by the speed of this shift.”
Until the mid-1990s, colon cancer was less deadly in people under 50 than brain cancer, leukemia, lung cancer, and breast cancer. It was only in 2021 when the US Preventative Services Task Force lowered the colon cancer screening age recommendation from 50 to 45, realizing that the risks had changed.
The absolute number of colon cancer deaths in working-age people under 50 is still relatively small, with the American Cancer Society estimates suggesting around 3,750 people under 50 died from colon cancer in 2023. But unlike those four other leading causes of cancer death, where Siegel said there’s “great news” to report, the trend lines with young colon cancer are going in the wrong direction.
The Pace of the Increase Surprised Seasoned Cancer Experts
Something unique appears to have happened to the cohort of people born after 1950, and it’s putting every subsequent generation at a greater risk of developing colon cancer early and fast. Colon cancer has been the leading cause of cancer death in men under 50 since about 2014, when it beat out lung cancer, but until 2023, breast cancer remained the leading cause of cancer death in people under 50 overall.
“We weren’t expecting colorectal cancer to rise to this level so quickly, but now it is clear that this can no longer be called an old person’s disease,” Dr. Ahmedin Jemal, the study’s senior author, said. “We must double down on research to pinpoint what is driving this tsunami of cancer in generations born since 1950.”
Experts had been projecting that colon cancer would likely become the leading cause of cancer death for everyone under 50 years old at some point before 2030, but the pace of the increase surprised even the most seasoned cancer experts. To go from fifth to first place over the course of about two decades “is not typical in cancer research,” Siegel said. It’s remarkable it all happened within the lifespan of her young adult daughter, she said.
The Reasons for the Rapid Shift are Complex
The reasons for such a rapid shift are complex. While the rate of aggressive colon cancer cases has been going up, doctors have been getting better at treating and preventing other deadly cancers. Plus, lung cancer deaths plummeted, as people quit smoking en masse. Breast cancer is still the leading cause of cancer death in women under 50, when men are left out of the equation, but the number of women dying of breast cancer every year has also gone down steadily since the mid-1990s.
As News Nation reports, experts aren’t exactly sure why colon cancer death rates are soaring, but point to a likely mix of complex factors influencing our environment, our genetics, and early life exposures during a baby’s first months in and out of the womb.
Previous findings from the ACS, as well as the opinions of medical experts, attribute at least some instances of colon cancer in young adults to “diet, decreased exercise and poor lifestyle choices like increased smoking or drinking,” Dr. Dana Hayden, a colon and rectal surgery specialist with UW Health in Madison, Wisconsin, said in 2023. “But there are definitely some other factors that could be related to genetics, that could be related to tumor biology,” said Hayden said. “So we are trying to work very quickly to figure this out.”
The results of a study published in August 2025 also indicated a massive 50% spike in colon cancer diagnoses specifically among adults ages 45 to 49, Nexstar’s KXAN reported. But at least part of that percentage was due to a spike in diagnoses made after the first year of the COVID-19 pandemic, which may have delayed patients from seeking more prompt medical opinions.
The ACS researchers behind that study, too, said there were numerous possible reasons for diagnosis rates. “There’s a wealth of research happening in this area right now looking at all kinds of factors such as diet, family history, even early-life exposures like antibiotics,” Dr. Rajesh Shah, of Baylor Scott & White Gastroenterology, told KXAN. “There will be a lot of interesting studies coming out in the next 5-10 years to give us a better sense of this.”
Regular Colonoscopies & Early Detection are Key
Prevention isn’t as simple as the old standard advice to eat a healthy diet and get enough exercise, though those factors are still part of the equation. The air we breathe, the foods we consume, and the movement we do all play a role, but there seems to also be an element of luck involved. For example, one twin may get colon cancer, while another shows no signs.
Experts have a few key pieces of advice. Everyone should start getting colonoscopies at age 45. They aren’t just screening tools, they are also intestinal housecleaning measures, designed to remove precancerous polyps before cancer develops. People with a family history of colorectal cancer, or those with certain bowel conditions, may want to be screened even earlier, the Centers for Disease Control and Prevention (CDC) suggests.
Additionally, medical experts do say to limit alcohol consumption and eat plenty of fiber, especially from foods like leafy greens, other vegetables, and whole grains. And if you see blood in the toilet, or have persistent stomach pain for weeks and weeks that will not go away, get it checked out.
“This research underscores the urgent need to protect and expand access to care, especially at a time when increasing health care premiums and cuts to prevention and screening programs threaten to reverse our progress and undo the gains we have achieved,” Lisa A. Lacasse, the president of the American Cancer Society Action Network, said of the organization’s recent findings. “We cannot afford to turn back the clock now.”
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