Dr. Frank Frizelle has operated on countless patients in his career as a colorectal surgeon. But there’s one case that stayed with him.
In 2014, he was treating a woman in her late 20s suffering from bowel cancer—already a rare situation, given her age. But it became even more unusual when her best friend visited her in the hospital and told Frizelle that she had many of the same symptoms as his patient. Subsequent testing revealed that his patient’s friend had a lesion that, had it not been caught early, likely would have become cancerous. “That really brought it home to me—how it’s much more common than you think,” says Frizelle, a professor of surgery at the University of Otago in New Zealand.
Still, like any good scientist, Frizelle was skeptical. Was it simply a fluke that he kept treating strikingly young patients? Or was his practice one tiny data point in a larger trend?
He found his answer after sifting through national health data: colorectal cancer, he discovered, was indeed being diagnosed more often than in previous years among New Zealanders under 50. Further research by Frizelle analyzing populations in Sweden and Scotland showed the same thing. A bigger picture was emerging. Here were three different countries, with different populations and health challenges—but united by a spike in colorectal cancers among young adults.
In the years since, it’s become clear that the problem isn’t limited to those three countries, nor to colorectal cancer. Researchers have found that young people around the world are getting many different kinds of cancer at alarmingly high rates. And as the diagnoses of celebrities and public figures like Kate Middleton, Chadwick Boseman, Dwyane Wade, and Olivia Munn bring mass attention to the issue, scientists are racing to answer a question on the minds of many outside the medical profession: Why is cancer, historically a disease of old age, increasingly striking people in the primes of their lives?
Globally, diagnoses and deaths related to early-onset cancers—those affecting patients younger than 50—rose by 79% and 28%, respectively, from 1990 to 2019, according to a recent study published in the medical journal BMJ Oncology. In the U.S., breast cancer is the most common type of early-onset disease, but recent surges in cancers affecting digestive organs—including the colon, rectum, pancreas, and stomach—are particularly dramatic within this age group. In fact, today’s young adults are about twice as likely to be diagnosed with colon cancer—and four times as likely to be diagnosed with rectal cancer—as those born around 1950, research suggests.
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Overall, cancer is still overwhelmingly an older person’s disease. As of 2025, 88% of people in the U.S. diagnosed with cancer were 50 or older, and 59% were 65 or older, according to data from the American Cancer Society. But there is no question that the demographics are shifting. Under 50s are not only at increasing risk of suffering from cancer; theirs is the only age group for which the risk is rising. All told, 17 types of cancer are on the rise among U.S. adults in this age group.
“When we were younger, we assumed the climate would be the same forever. The same applies in cancer,” says Dr. Thomas Powles, a U.K.-based oncologist and cancer researcher who edits the journal Annals of Oncology. “We just assumed that cancer incidence was something that is relatively static. But it’s not.”
There is some good news in the data. Advances in disease detection and treatment, as well as dramatic declines in smoking, mean that far fewer people die from cancer now than once did. Although the disease still ranks as the second most common cause of death in the U.S., killing more than half a million people each year, mortality rates have dropped by about a third since 1991.
Less encouragingly, the rate of new cancers diagnosed has remained stubbornly consistent, declining only modestly from 1999 to 2021. Across the U.S., roughly 2 million new cancer cases are detected each year, diagnoses that, on top of the emotional toll, force patients to cumulatively fork out billions of dollars in out-of-pocket costs—more than $16 billion in 2019 alone, according to federal data. Today, about 40 out of every 100 U.S. adults can expect to be diagnosed with cancer at some point in their lifetimes. For an estimated 1 in 17 U.S. women and 1 in 29 U.S. men, that news will come before their 50th birthdays.
The rise in early-onset diagnoses partly comes down to advances in our ability to detect and diagnose different kinds of cancers. “With much more sophisticated tools now, inevitably we’re doing more tests on younger people [and] we’re using more accurate imaging,” which leads to more cancers detected, Powles says. Some screening protocols have also been modified in recent years to include younger adults; since 2018, for example, the American Cancer Society has recommended colonoscopies starting at age 45, down from 50.
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But this is only one part of what scientists say is a more complex web of factors they are still attempting to understand. The data suggest that some element—or perhaps combination of elements—of modern life is sickening progressively younger adults. And right now, no one knows for sure what that is.
There are plenty of known risk factors for cancer, from the genes someone is born with to the unhealthy lifestyle habits they pick up, such as smoking, drinking lots of alcohol, or spending time in the sun. Such habits can speed up the natural degradation of cells, which over time acquire genetic mutations as they lose their ability to repair damage. As that damage accumulates with age, cells may become cancerous, growing and -multiplying too fast for the body’s immune system to keep them in check and potentially choking out vital organs. The immune system also loses some of its strength with age, making it easier for cancer cells to colonize the body.
But classic risk factors do not seem to fully explain the recent rise in early-onset cancers, says Dr. Cathy Eng, director of the Young Adult Cancers Program at Vanderbilt University’s Ingram Cancer Center in Tennessee. Some of the trends are baffling; young, nonsmoking women, for example, are being diagnosed with lung cancer in strangely high numbers. Many times, Eng’s patients were extremely healthy: vegetarians, marathon runners, avid swimmers. “That’s why I really believe there’s other risk factors to account for this,” she says.
There’s no shortage of theories about what those may be. Many scientists point to modern diets, which tend to be heavy on potentially carcinogenic products—including ultra-processed foods, red meat, and alcohol—and may also contribute to weight gain, another cancer risk factor. The foods we eat can also affect the gut microbiome, the colony of microbes that lives in the digestive system and appears linked to overall health. Alterations to the gut microbiome via diet, or perhaps exposure to drugs like antibiotics, have also been implicated.
Other researchers blame the microplastics littering our environment and leaching into our food and water supplies, some of which, according to a 2024 study, have even shown up in cancer patients’ tumors. Other environmental factors could also be to blame, given that everything from cosmetics to food packaging contains substances that many researchers aren’t convinced are safe. Even our near constant exposure to artificial light could be messing with normal biological rhythms in ways that have profound health consequences, some research suggests.
For now, these are all just hypotheses. Some may turn out to be wrong, and more theories will emerge in time. It’s also likely that different risk factors are linked to different cancers, Frizelle says. Even in a single patient, multiple overlapping triggers may be in play.
Frizelle’s research on colorectal cancer, for example, suggests there may be a dysfunctional relationship between microplastics, certain foods, and some types of gut bacteria. Studies suggest that when microplastics get into the body, they can penetrate the mucous lining that protects the bowels and carry bacteria and toxins to the bowel lining. This leaves the bowel more susceptible to damage from pathogens inside the body—including strains of gut bacteria that are known to become more virulent when they interact with compounds found in red and processed meat. In some patients, this perfect storm of invaders may result in cancer, Frizelle thinks.
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He believes this overlapping puzzle of risk factors is a likelier explanation than any one lifestyle habit driving a dramatic uptick in cancers—especially since younger generations are, in many respects, healthier than their ancestors. In the U.S., for example, tobacco use has plummeted in recent decades, and young adults are increasingly unlikely to drink. “How is the health-conscious generation getting more bowel cancer?” Frizelle asks.
Dr. Andrea Cercek, co-director of the Center for Young Onset Colorectal and Gastrointestinal Cancers at Memorial Sloan Kettering Cancer Center in New York City, agrees that some early-onset cancer cases defy easy explanation. She’s treated patients in their 20s and even teens with tumors that, biologically, “look just like a regular 80-year-old’s tumor.” These cases stump her. “Even if they drank as a teenager, it just doesn’t make sense,” she says. A few years of drinking alcohol, following an unhealthy diet, or having obesity should not be enough to produce the kind of tumor typically seen in a senior citizen, Cercek says. And yet, there they are.
To Cercek, these advanced tumors suggest that people have been exposed to damaging substances for a long time, perhaps even longer than they were aware of. Research and awareness about early-onset cancer is accumulating now, but the source of the problem may not be new, Cercek says. It can take years for even the most toxic exposures to result in health problems—which means that the source of a problem in the public eye now may have emerged decades ago, silently sickening people until the trend became too pronounced to ignore.
Giancarlo Oviedo-Mori, 32, is one of many patients whose cancer defies obvious explanation. When he was in high school, Oviedo-Mori developed a persistent cough that didn’t respond to medication. Eventually, at just 18 years old, he was diagnosed with Stage IV lung cancer.
Oviedo-Mori and his doctors were stunned. He’d had asthma as a child growing up in Peru, but he had no family history of cancer and had never been a drinker or smoker; he was barely even old enough to buy cigarettes and still years shy of his 21st birthday. Oviedo-Mori’s family spent a day observing the site of the 9/11 terrorist attack when toxic particles were still in the air, but it had been a brief visit and no one else in the family had developed health problems. That was the only exposure he could think of. The diagnosis didn’t make sense. “It was so weird,” he says.
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As he went through cancer treatment—including chemotherapy, radiation, and a surgery that removed his entire left lung—he’d look at his fellow patients, and, seeing how much older they were, feel out of place. “I didn’t belong there,” he says.
More than a decade later, Oviedo-Mori is still in treatment, participating in a clinical trial at Memorial Sloan Kettering (where all the patients pictured in this article have received care) in hopes of ridding his body of cancer for good. But, though he’s still fighting cancer, he is in good health—he can even play soccer, despite having only one lung, and chase after his almost 2-year-old son. “Sometimes, I don’t believe it,” he says. “I think about [my son] and I’m like, ‘Oh my gosh, you’re really a miracle.’”
Figuring out how young people like Oviedo-Mori fall prey to cancer is not easy, given the sheer number of potential health hazards in the modern world. It is a puzzle with an unknown number of pieces—one that Dr. Shuji Ogino, a pathologist at Brigham and Women’s Hospital in Boston, is trying to solve with a technique he pioneered.
Ogino and his team are making their way through about 4,000 colorectal tumor samples that came from people who developed the disease at various points in their lives. Each sliver of tissue holds innumerable clues about the person it belonged to, from what they ate and drank to the bacteria that lived in their body before cancer took root. To unearth these clues, the researchers stain the tissues, so that under the lens of a powerful microscope, they can see the different types of cells in the tumor in brilliant color. Using these cell-level insights, they can distinguish between the tumors of young vs. older patients and—with the help of AI—search reams of scientific literature for environmental exposures, lifestyle habits, or health conditions linked to particular cellular traits. Repeating this painstaking detective work enough times helps reveal patterns among young cancer patients, giving Ogino and his team clues as to what may have caused their diseases.
Their research has already pointed to some possible answers for early-onset colorectal cancer. The big three so far are eating a typical Western diet (high in sugar, processed foods, and red meat, low in fresh produce), developing insulin resistance (a precursor to diabetes also linked to poor diet), and having a particular type of E. coli bacteria in the gut. Nothing is proven yet, Ogino says. But since there’s no harm in eating healthfully, he believes dietary changes are worth making now.
Ogino personally drinks very little and eats a healthy diet. He makes sure his young son eats well too, since his research makes him acutely aware of the importance of developing healthy habits starting from a very young age. But even for children as young as Ogino’s son, some damage may already be done—at least according to Dr. George Barreto, a surgeon and cancer researcher at Flinders University in South Australia.
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Barreto—who started researching early-onset cancer after not just his patients, but also several of his relatives and friends, were diagnosed at young ages—has theorized that damage may start in the womb. It’s well established that the pre-natal period can have long-term effects on a baby’s health, and Barreto believes that phenomenon may extend to cancer risk if parents are exposed to carcinogens during this critical developmental time. This theory could help explain mysterious cases like those Cercek describes, involving patients who seemingly haven’t lived long enough for even their riskiest habits to catch up with them.
Proving his theory won’t be simple, Barreto acknowledges. It would require collecting data on huge numbers of people, starting before they were even born, then sifting through that data to pinpoint relevant prenatal and early-life triggers. To speed up the process, Barreto has contacted more than 20 research groups around the world that are tracking groups of people beginning at or before birth, in hopes of using their data to jump-start his research. “If we start [from scratch] now, it will take us 40 years to find answers,” Barreto says. That’s too long to wait, with patients already getting sick at an alarming rate.
There is yet another question for researchers to answer: whether, on a molecular level, young patients’ cancers are dramatically different from those that occur in older people. If so, these findings may guide researchers toward new treatment approaches.
Some research, including by Eng, has pointed to molecular differences, at least among patients with early-onset colorectal disease. But other scientists are less convinced. Powles, the U.K. oncologist, says he hasn’t seen strong evidence to suggest that early-onset cancers are much different or more aggressive than later-in-life cancers; they just happen to strike patients at younger ages.
Even if there is no medical requirement to stray from classic treatment methods—like chemotherapy, radiation, and surgery—younger patients have unique needs. Standard treatments, while often effective, can be destructive for people with decades of life ahead of them, potentially leading to life-altering physical changes, like permanently needing a colostomy bag or enduring early menopause and infertility. “The worst thing [for an oncologist to hear] is, ‘I’m cured and my cancer’s gone, but I wish that I’d just lived with my cancer because living like this isn’t living,’” Cercek says.
Kelly Spill was blindsided when she was diagnosed with Stage III colorectal cancer in 2020. She was only 28, had no family history of colorectal cancer, and had recently given birth to her first child. She was even more stunned when she learned that her treatment would force her to permanently use a colostomy bag and leave her unable to carry more children. “That completely broke me,” she says. “I’d always wanted a big family.”
Just before she was set to start chemotherapy, however, a research nurse told her she might be a fit for an experimental trial that Cercek was leading. Cercek was testing a new approach among patients whose tumors had a specific genetic mutation: using intravenous medication to boost their immune systems’ abilities to recognize and attack cancerous cells, ideally sparing patients from chemotherapy, radiation, and surgery.
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Despite all the unknowns that came with participating in a clinical trial, Spill says it was a “no-brainer” to try Cercek’s approach instead of therapies that would leave her with lifelong physical side effects. Her gamble paid off: by her ninth treatment session, her tumor had entirely disappeared. Spill is still cancer-free and expecting her third baby in May.
In June, Cercek reported that out of 41 rectal cancer patients who completed the full regimen, 100% were cancer-free and required no additional treatment. She is now also studying the method against a variety of different cancers, ranging from stomach to bladder. A patient of any age could benefit from this approach, Cercek says, but it could be particularly impactful for young patients, like Spill, who are desperate to avoid permanent side effects.
Even without novel medical approaches, cancer centers are beginning to recognize that, compared with elderly patients, “adolescents and young adults have very different experiences, and therefore need very different approaches to their treatment,” says Alison Silberman, CEO of Stupid Cancer, a nonprofit that supports young people with the disease. Physical fallout isn’t the only hurdle to overcome, Silberman says. Compared with older patients, young people are more likely to struggle to pay for their care and to develop mental-health issues as a result of it.
Silberman witnessed these challenges when her brother was diagnosed with advanced cancer in his 20s. “He was yanked out of his life,” forced to leave his job and apartment to move back in with their parents, Silberman remembers. Cancer made him grapple with his own mortality, largely on his own. “He was too old to be a pediatric patient, too young to be an adult patient,” she says. “That was very isolating for him.”
“Care of early-onset cancer patients becomes complex even beyond [medicine],” says Dr. Veda Giri, an oncologist and co-director of Yale Cancer Center’s Early Onset Cancer Program in Connecticut. This spring, the program will launch new services meant to address that very problem. Patients in the program will be contacted by coordinators who can help guide them through issues that commonly affect young-adult patients, from ways to preserve fertility to deciding whether to pursue genetic testing or enroll in a clinical trial. Patients can also participate in support groups with others in their age group, in hopes of improving social and mental health. The goal: to “support patients and their families from diagnosis all the way through their cancer journey and beyond into survivorship,” since young adults cured of cancer may have continuing needs for decades to come, Giri says.
The ultimate goal, of course—and the ultimate win for doctors and researchers working in this field—will be for early-onset cancer centers to be rendered unnecessary. But it likely won’t happen anytime soon. Proponents of sophisticated new artificial-intelligence technologies have raised expectations, promising new tools that could transform cancer research. AI gives scientists the ability to sift through mountains of data with hitherto unimaginable levels of precision. And the hope is that these tools will unlock a cascade of new discoveries—illuminating unrecognized risk factors, for example, and turbocharging the development of new treatments.
But cancer researchers remain cautious. There is hope, no doubt—but like the legions of scientists grappling with complex medical puzzles in other fields, they are wary of overstating the pace of progress and raising the hopes of patients, even with new technologies at their disposal.
“It will be impossible to design a clinical trial that can test all different possible causes of early-onset cancer,” says Dr. Andrew Chan, director of cancer epidemiology at Mass General Cancer Center. AI and other technologies may help land on those possible causes faster. But to really understand exactly what’s driving the disease and how to stop it, researchers must work slowly and methodically, studying various potential triggers—from diet to alcohol to microplastics—one by one.
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Chan’s team is starting with a trial that will study whether losing weight with the help of GLP-1 drugs like Wegovy and Zepbound affects future cancer risk among people who have survived early-onset cancer and who are overweight. Future research may study the effects of specific dietary changes, he says. But not all potential cancer triggers are as straightforward to modify as weight and diet.
Take microplastics, which Frizelle, the New Zealand surgeon, believes are contributing to early-onset cancer. Frizelle is realistic about their ubiquity. Avoiding them is all but impossible in a world where water supplies are tainted and babies suckle on plastic bottles from their earliest days on earth. Barreto’s research on cancer risk starting in the womb paints an even bleaker picture, suggesting that the deck may be stacked against some people before they are really people at all. (He chooses to see it more optimistically, noting that everyone can still “take the power into their own hands” by avoiding known carcinogens.)
The upshot of all this: it could take years, if not decades, to sort out what’s causing early diagnoses, and perhaps even more time to figure out how to stop them. What seems so obvious to us now—the conclusion that smoking cigarettes causes lung cancer, for example—took some 40 years for scientists to solidify. Even once they did, change didn’t happen overnight. Smoking rates have fallen steadily since public-health warnings escalated in the 1960s, but they didn’t plummet all at once. Still, change is possible. Today, smoking is at historic lows, and lung cancer diagnoses have declined with them.
If the challenge sounds daunting, for researchers like Ogino, from Brigham and Women’s, the complexities are part of the process. He is reminded every day that good science takes as long as it takes. Many of the tumor samples he relies on in his research came from participants enrolled in a study that launched in 1976. The researchers who started it couldn’t have known that, 50 years later, their work would be critical in the quest to reverse the rise of early-onset cancer, Ogino says.
“That’s the kind of legacy you can make in science,” he says. “That’s a great, rewarding way to contribute”—even if it takes a lot of time to get there.