Cancer cases in both younger and older adults are increasing, challenging the idea that a global rise is only occurring in the under 50s, a major new analysis has found.
An international study, led by scientists at The Institute of Cancer Research, London, found that cancer incidence increased over a 15-year period in both older and younger adults in most (75 per cent) of the 42 countries, for five of the 13 cancers they looked at.
The results of the analysis, published in the journal Annals of Internal Medicine, showed that rates of thyroid, breast, kidney, endometrial and leukaemia cancers for younger adults had increased. Trends in adults over 50 were not significantly different from the under 50s for these five cancers.
Trends in bowel cancer were unique
However, trends in bowel cancer were unique as incidence rates increased at a faster rate in younger adults more than in older adults in approximately 30 per cent of the countries studied.
For liver, oral, oesophageal and stomach cancer, incidence rates decreased in younger adults in more than half of the countries studied contrary to previous reports that these cancers were also part of the global epidemic of early onset cancer.
For the other three cancers that were previously identified as part of the global epidemic of early-onset cancer – gallbladder, pancreatic and prostate – no clear patterns of widespread increases were found.
There has been growing concern about a potential global epidemic of cancer in younger adults following several studies that have reported increasing cancer incidence rates in the under 50s in many countries (see notes to editors). A wide range of potential causes have been suggested such as changes in diet, childhood obesity and antibiotic use.
Previous studies didn't look at older adults
However, previous studies of international trends have mostly restricted their evaluation to cancer incidence in under 50s and have not directly compared these trends with those in older adults.
The Institute of Cancer Research (ICR) team’s approach was to systematically compare the direction and magnitude of recent trends in cancer incidence in younger (20-49 years) and older adults (50-69 years) across 42 countries, over a 15-year period between 2003-2017. The research team looked at 13 cancers that previous studies had reported to be increasing in younger adults in many countries.
They compared the annual cancer incidence data in the World Health Organisation’s International Agency for Research on Cancer GLOBOCAN database.
The authors point out that cancer continues to be a disease that predominantly affects older people. In 2019, there were about 36,000 cancers diagnosed in people under 50 in the UK. There were nearly 10 times more (about 350,000) cancers diagnosed in older people.
'Whatever is triggering the rise in these cancers is more likely to be common across all age groups'
Study leader Professor Amy Berrington, Team Leader in Clinical Cancer Epidemiology at The Institute of Cancer Research, London, said:
“Our findings suggest that whatever is triggering the rise in these cancers is more likely to be common across all age groups, rather than specific to cancers in the under 50s, since there were similar increases in younger and older adults.
“There is a risk that resources for research and intervention may be misallocated if attention is focused only on the increases in cancer in young people. The stats continue to show that cancer is a disease predominantly affecting older people.
“In our study, bowel cancer is the only cancer found to be increasing in many countries in younger adults faster than it is in older adults.
“It’s possible that this difference could be due to routine bowel screening offered to older adults. Bowel cancer screening not only helps to detect cancer at earlier stages but also helps prevent cancer through the removal of pre-malignant lesions. This could be why bowel cancer cases seem to be rising faster in younger adults – we’re getting better at preventing them developing in older adults.
“Several studies have suggested that rising rates of obesity could be behind the increases in cancer in younger adults. The cancers that we identified as increasing are all obesity-related cancers, including endometrial and kidney cancer. We are currently investigating how much of the increase could be explained by obesity, or whether novel carcinogens may also be involved – so far, the evidence is unclear.”
'These findings cast doubt on the idea that the rise in cancer rates is only affecting younger people'
Professor Kristian Helin, Chief Executive of The Institute of Cancer Research, London, said:
“This study shows that cancer incidence is rising in both younger and older adults – with the exception of bowel cancer – and that the rates of increase are broadly similar across multiple countries.
“In recent years, there has been considerable concern about a potential global epidemic of cancer cases in younger people. These findings provide a clearer picture of what is happening and cast doubt on the idea that the rise in cancer rates is only affecting younger people. It highlights the importance of including all adults, not just younger adults, when developing new guidelines and research strategies to address the increases in cancer incidence.”