Anthony Ellison was not particularly concerned when he went to see his GP for persistent diarrhoea. Then 39, the personal trainer had always been active and healthy.
“We did the normal investigations initially and cancer wasn’t even discussed – he thought it was a bug that hung around for a bit,” Ellison recalls. When a faecal occult blood test, which tests for traces of blood in the stool, returned three positive results, haemorrhoids were presumed the most likely culprit.
It wasn’t until a colonoscopy and a CT scan that the bad news was revealed, on the second-last day of his 30s: Ellison had stage 4 bowel cancer, with 20 metastases to his liver. “Obviously my 40th birthday party was pretty ordinary,” he says.
“Cancer obviously wasn’t on the radar, nor was any sort of chronic illness,” Ellison says. “In your 30s … you’re trying to build a family, you build a career and everything stops.”
Ellison’s experience is not the rarity it once was. In Australia, 10.7% of bowel cancer – also known as colorectal cancer – diagnoses now occur in people under 50.
Globally since the 1990s rates of certain cancers have increased markedly in younger people, prompting some researchers to label early-onset cancer as “an emerging global epidemic”.
A review of cancer registry data, published last year, found the incidence of 14 cancers – including colorectal, oesophageal, endometrial, gall bladder, kidney and thyroid – in under-50s had increased significantly in the past three decades in Australia, New Zealand, US, England and Wales, Canada and South Korea. The study observed a birth cohort effect, in which successive age groups had a higher cancer risk than their counterparts in earlier generations.
Better screening may have contributed to the rise in rates to a certain extent, the researchers noted, but “a genuine increase in the incidence of early-onset forms of several cancer types also seems to have emerged”.
Scientists hypothesise that the rise in early-onset cancer may be the result of changing lifestyles and different exposures to risk factors in early life and young adulthood – but unanswered questions about the underlying causes have prompted calls for urgent research.
Too young for cancer?
For younger Australians, the growth in cancer rates has been “appreciably greater than population growth”, a 2021 Australian Institute of Health and Welfare report noted. In the previous two decades, the incidence of bowel cancer in 20- to 39-year-olds more than doubled, from 4.4 to 10.3 cases per 100,000 people. Over the same period, thyroid cancer rates jumped from 6.5 to an estimated 10.9 cases per 100,000.
Last year, a study of South Australian cancer data found that rates of gastrointestinal adenocarcinomas – cancers that develop in the glands lining the oesophagus, stomach, pancreas, colon and rectum – rose significantly between 1990 and 2017 in those under 50. For those older than 50, the rates have been dropping since 2000.
“There are some cohorts of people who have a higher incidence than average,” says Dr Savio Barreto, an associate professor in medicine at Flinders University, who led the research. “In our South Australian population, it was [young] males.”
Despite the changing demographics, age remains one of the biggest risk factors for cancer, says Dr Eleonora Feletto of the Daffodil Centre. “In quite a few cancers, 50 is where your risk starts to increase.”
Because cancer is still seen predominantly as a disease of old age, younger patients who don’t fit the typical clinical picture can face months-long delays before being accurately diagnosed.
This was the experience of Stephanie Bansemer-Brown, who presented to her doctor with symptoms about 18 months before she was diagnosed with stage 3 bowel cancer, aged 41. “I had blood in my stool, I had bloating, I was very tired.”
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Bansemer-Brown, who now works for Bowel Cancer Australia, was initially told she had haemorrhoids from the recent birth of her son. When, months later, she requested a colonoscopy, her doctor told her she was too young to have cancer.
“There shouldn’t be an age bias,” she says. “I was a fit, healthy woman. I didn’t drink excessively, I didn’t smoke, I ate well, I exercised moderately. ‘Why’ is the question.”
‘What we put into our mouths, what we breathe’
While researchers do not have a definitive answer, they believe the rise in early-onset cancer is linked to changing diets, lifestyles and environmental exposures over several decades.
The western diet – higher in red and processed meat, saturated fat, sugar and processed food – has spread globally in the past half century. Obesity, rates of which have nearly tripled globally since 1975, according to the World Health Organization, has been linked to multiple cancer types, including colorectal, thyroid, pancreatic and ovarian cancer.
“I think the change is going to be [down to] a mixture of environmental factors – what we put into our mouths, what we breathe, but also genetic factors,” says A/Prof Graham Newstead, the medical director of Bowel Cancer Australia. “Most of the cancers that occur in the under-50 group are not on the background of a family history.”
Scientists are also gaining understanding of the connection between the microbiome – the community of microbes such as bacteria, fungi and viruses that live in and on our bodies – and cancer development. The microbiome shapes our health in myriad ways, playing a key role in digestion and regulating immunity and inflammation. It can be altered by factors including diet and exercise.
Of the 14 cancers analysed in the 2022 international review, eight were related to the gastrointestinal system.
That finding makes sense, says Prof Emad El-Omar, the director of the Microbiome Research Centre at the University of New South Wales, because “most of the microbiome is in the digestive system”. The increased consumption of processed food in our diets – with more additives such as emulsifiers and artificial sweeteners – has an adverse impact on microorganisms, he says.
Using antimicrobials also has an effect. “There’s no doubt that over the last few decades we’ve been prescribing more antibiotics for less appropriate indications,” El-Omar says. “The period when this is most important is probably [in childhood] when you try to establish the stable microbiome that you stay with.”
Antibiotic use per capita is up globally since 2000 and research has found a correlation between “excessive or prolonged use of antibiotics” and a slight increase in the risk of some cancers.
The timing of exposure to risk factors may be an important factor, Barreto says. He and Stephen Pandol of Cedars-Sinai Medical Center have proposed that the risk for early-onset cancer could begin as early as in the womb, as a result of exposure to stressors during the perinatal period. “We’re yet to prove it, but we’re working on it,” he says.
Now 43, Ellison has had several surgeries. In recent months, his daughter Olive has watched him undergo palliative chemotherapy, peppering him with questions: “‘Why does it have to be you, why can’t it be another person? Will it go away? … Are you going to die?’ These are full-on conversations to be having with a seven-year-old.”
Some weeks – particularly when he has chemo – are harder than others, but he is able to continue training clients and has rediscovered his love for drumming. Every few weeks, he takes a short holiday with his family.
“Once you get the idea of your own mortality and you accept it, you start to find other positives,” Ellison says. “You find joy in the simple things.”
