The sharp increase in cancer diagnoses among young adults is alarming the medical profession, with scientists intensifying their efforts to determine what’s driving the baffling rise.
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 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, probably 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 sceptical. Was it simply a fluke that he kept treating strikingly young patients? Or was his practice one tiny data point in a larger trend?
TIME Magazine reports that 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 analysing 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 worldwide are getting many different kinds of cancer at alarmingly high rates.
Now, 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 under 50 – rose by 79% and 28%, respectively, from 1990 to 2019, according to a study in BMJ Oncology.
In the US, 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.
Overall, cancer is still overwhelmingly an older person’s disease. As of 2025, 88% of people in America 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 US adults in this age group.
“When we were younger, we assumed the climate would be the same forever. The same applies in cancer,” said Dr Thomas Powles, a UK-based oncologist and cancer researcher who edits 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 US, 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 US, roughly 2m new cancer cases are detected each year, diagnoses that, on top of the emotional toll, force patients to cumulatively fork out billions in out-of-pocket costs – more than $16bn in 2019 alone.
Today, about 40 out of every 100 US adults can expect to be diagnosed with cancer at some point in their lifetimes. For an estimated one in 17 American women and 1 in 29 American 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 more sophisticated tools now, inevitably we’re doing more tests on younger people (and) using more accurate imaging, which leads to more cancers detected,’ Powles said.
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 45, down from 50.
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 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, like 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 colonise 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 Programme at Vanderbilt University’s Ingram Cancer Centre in Tennessee.
Some of the trends are baffling; young, non-smoking 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’re other risk factors to account for this,” she said.
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.
Plastics
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’ tumours.
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 said.
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.
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 US, 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 Centre for Young Onset Colorectal and Gastrointestinal Cancers at Memorial Sloan Kettering Cancer Centre 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 tumours that, biologically “look just like a regular 80-year-old’s tumour”.
These cases stump her. “Even if they drank as a teenager, it just doesn’t make sense,” she said. A few years of drinking alcohol, following an unhealthy diet, or having obesity should not be enough to produce the kind of tumour typically seen in a senior citizen, Cercek said. And yet, there they are.
Damaging
To Cercek, these advanced tumours 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 said.
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, he was diagnosed with stage 4 lung cancer.
Oviedo-Mori and his doctors were stunned. He’d had asthma as a child growing up in Peru, but 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.
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 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 two-year-old son.
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 tumour samples 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.
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.
Dr George Barreto, a surgeon and cancer researcher at Flinders University in South Australia, has theorised 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.
Barreto has contacted more than 20 research groups worldwide 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 said.
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 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 UK 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.
Colostomy
Kelly Spill was diagnosed with stage 3 colorectal cancer in 2020 took part in Cercek's new approach among patients whose tumours had a specific genetic mutation: using intravenous medication to boost their immune systems’ abilities to recognise and attack cancerous cells, ideally sparing patients from chemotherapy, radiation, and surgery.
Spill's gamble paid off: by her ninth treatment session, her tumour had entirely disappeared. Spill is still cancer-free and expecting her third baby in May.
Last 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.
Even without novel medical approaches, cancer centres are beginning to recognse 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 non-profit that supports young people with the disease.
Dr Andrew Chan, director of cancer epidemiology at Mass General Cancer Centre, 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.
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.
TIME Magazine article – The Race to Explain Why More Young Adults Are Getting Cancer (Open access)
See more from MedicalBrief archives:
Alcohol consumption linked to rising cancer cases – US study
Millennials and Gen Xers have higher risk of 17 cancers – US study
Cancer diagnoses among younger people rising
Global quest to pinpoint cause of early-onset cancers
Vital early signs of colon cancer in young adults – US study