22 Jun 2023 Alarming rise of early-onset cancer among millennials
Researchers are unsure of the exact reasons behind this trend but suspect changes in nutrition, lifestyle, and the microbiome may play a role. The rise in early-onset cancers has economic, clinical, and social implications, necessitating further research and potential adjustments to screening programs.
Increasing numbers of younger people in the developed world are being diagnosed with the disease. Scientists are not sure why.
The past 30 years have seen an upsurge in cases of so-called “early onset” cancer in the under-50s. So marked is the increase leading epidemiologists have suggested it should be called an epidemic.
Financial Times analysis of data from the Institute for Health Metrics and Evaluation at the University of Washington School of Medicine shows that over the past three decades, cancer rates in the G20 group of industrialised nations have increased faster for 25- to 29-year-olds than any other age group — by 22 percent between 1990 and 2019. Rates for 20- to 34-year-olds in these countries are now at their highest level in 30 years.
In contrast, cases in older age groups — those over 75 — have declined from their peak around the year 2005.
Over the past three decades, cancer rates have risen faster for 25-29 year-olds than any other age group
Researchers have no definitive explanation for why people in the prime of life seem to be markedly more vulnerable to the disease than their counterparts in earlier generations.
There may be clues in the types of cancer afflicting the young, researchers believe. Among 15- to 39-year-olds, cases of colorectal cancer increased 70 percent in G20 nations between 1990 and 2019, compared to a 24 percent increase in all cancers, the FT’s research found.
Analysis produced by the American Cancer Society based on national data on cancer incidence and mortality suggests that this year 13 percent of colorectal cancer cases and 7 percent of deaths will be in people under 50.
Michelle Mitchell, chief executive of Cancer Research UK, or CRUK, cautions that age remains the biggest predictor of cancer risk, with around 90 percent of all cancers affecting over-50s and half afflicting those over 75.
But the increase in younger age groups is nevertheless “an important change. We need to understand that change,” she says. CRUK has launched a joint research initiative with the US National Cancer Institute to learn more about the causes of early-onset cancer.
Incidence rates of some cancers have soared since 1990 for 15- to 39-year-olds.
The trend has economic, clinical, and social implications. For cancer doctors on the frontline, the rise in such cases is becoming an inescapable and worrying aspect of their practice. Shahnawaz Rasheed, the surgeon in charge of Scott’s treatment at the Royal Marsden, a renowned London cancer hospital, recalls a two-week period a couple of years ago when he operated on four women under 40. Another recent patient was a super-fit international sportswoman in her 30s.
Diagnoses in young adults hit clinicians like Rasheed hard, deepening his resolve to find answers. “These are people who should just be getting on with their lives… building careers, bringing up children,” he says. “It breaks my heart.”
The microbiome’s role
Scientists searching for insights are increasingly convinced that changes to nutrition and ways of living that began in the middle of the last century hold at least part of the key to the puzzle.
Dr Frank Sinicrope, an oncologist and gastroenterologist at the Mayo Clinic in the US with a particular interest in early-onset colorectal cancer, says the incidence of the disease has been markedly increasing among people born in or after the 1960s. The increase in younger people coming to him for treatment in recent years has been “quite alarming,” he says.
The diet and lifestyle to which children are exposed in early life are likely to be a factor in the rise, he says, pointing to childhood obesity which has “become more prevalent and more problematic over the past 30 years.” However, no single factor can explain it, Sinicrope adds.
As they explore a connection with diet, researchers are homing in on the possibility that changes to the microbiome—the roughly 100tn microbes that live inside us, mostly in the gut—are increasing susceptibility to cancer. The microbiome is thought to play a key role in overall health, including digestion and regulation of the immune system, as well as protecting against disease-causing bacteria and aiding the production of vital vitamins.
The consumption of food high in saturated fat and sugar is believed to alter the composition of the microbiome in ways that can harm an individual’s health. While these changes affect people of all ages, researchers believe it is highly significant that cases of early-onset cancer started to rise around 1990. People born in the 1960s belonged to the first generation exposed from infancy to modernised diets and lifestyle and environmental changes that started to become the rich-world norm in the 1950s.
The fastest increase has been in 15-39 year-olds in upper-middle income countries
Cancer often develops over decades—people can harbour slow-growing tumours for years—so for those diagnosed in their twenties, thirties, and forties, “some of the risk factor exposures may have happened when they were a baby or even in utero,” says Prof Shuji Ogino, an epidemiologist at the Harvard TH Chan School of Public Health who is part of the CRUK/NCI research initiative.
The fact that the biggest increases in cancer in the young have been in gastrointestinal varieties—colorectal as well as in the oesophagus, stomach, pancreas, bile duct, liver, and gallbladder—bolsters the case for a link with diet.
Some other cancer types increasingly seen in younger people, such as breast, kidney, and endometrial cancers, plus the blood cancer myeloma, may be affected both by obesity and the condition of the microbiome, even though they lack an obvious link to the digestive system, Ogino says.
Additionally, antibiotic use and medications more generally can affect an individual’s microbiome, sometimes referred to as their “bacterial fingerprint.”
Ogino points out that during the second half of the 20th century, the range of medicines available to treat multiple conditions substantially increased.
New anti-obesity medicines are a recent example. “The effect really remains unknown what they all do in the long term,” Ogino says.
The link to the microbiome is still circumstantial, he emphasises. He points to other changes that occurred from the 1950s onwards: more sedentary lifestyles, changes to sleep patterns, and repeated exposure to bright light at night that can affect circadian rhythms and metabolism.
“All these changes are happening in a really parallel way, so it’s hard to tease out the culprit. There are likely multiple culprits which work together,” he says…..
The Financial Times, via BizNews.com: Read the full article here