Doctors may have moved one step closer to revealing why colorectal cancer cases are surging among younger adults.
A mysterious rise in cases among under-55s has sparked concerns in medical circles, especially as the cancer is being spotted among healthy youngsters who ‘run marathons’ and watch their diet.
Now doctors at Georgetown University, in Washington D.C., say the uptick could be linked to changes in young people’s gut microbiomes.
They found that tumors from younger patients were more likely to contain the fungus Cladosporium sp. when compared to older patients.
The fungus is only occasionally found in the human gut, where it is suspected to be an invader that does not aid in digestion. The fungus is also known to cause infections of the skin and nails.
Scientists have moved one step closer to understanding why there is a rise in colorectal cancer cases among young people (stock)
Colorectal cancer is the third most common cancer diagnosed in the United States, according to the National Cancer Institute. And it’s surging in young people.
About 153,000 Americans are diagnosed with colorectal cancer every year, of which 19,550 are under 50 years old.
Rates in the under 55s have doubled since the 1990s, which is raising concern among health professionals.
A 2023 report from the American Cancer Society, for example, states that the rate of colorectal cancer in Americans younger than age 55 increased from 11 percent of all cases in 1995 to 20 percent in 2019.
Dr Benjamin Weinberg, a gastrointestinal cancer expert, told AXIOS: ‘A lot of people blame obesity and diabetes.
‘But we have these patients who run marathons and they eat [healthy diets] and they’ve got very advanced colorectal cancer.’
For the study, scientists looked at tissue samples from 63 patients aged either under 45 years old or over 65 years.
They checked the DNA of microorganisms in the tumors to look for any differences in the gut microbiome.
This revealed that Cladosporium sp. was more common in the tumors of young patients than the older individuals.
The researchers also evaluated bacterial factors that could be in play.
There was no difference for most bacteria, such as Fusobacterium nucleatum, which was found about 30 percent of the time in both groups.
Other bacteria were also shown to be more common in the tumors of older patients.
It’s still unclear how Cladosporium sp. could lead to this increase in cases, but the researchers think it could damage cell DNA. This could make them turn into cancerous cells.
The results are to be presented next week at the American Society of Clinical Oncology’s annual meeting in Chicago, Illinois.
The researchers say their paper may have brought doctors one step closer to understanding what is causing the rise in colorectal cancer cases.
Dr Weinberger added: ‘There was some sort of exposure we think in the 1970s or 1980s — maybe everybody started taking antibiotics for ear infections or they stopped breastfeeding.
‘Something happened where this cohort is seeing this rise and we don’t know why.’
Previous theories have suggested that unhealthy diets, alcohol consumption and the rise of sedentary lifestyles could be behind the uptick.
But scientists say these do not explain why other cancers have remained flat or continued to tumble in under-55s at the same time.
All tumors contain bacteria and can also contain fungi, although these are not typically present.
Part of the surge could be that people are also more likely to have their colorectal cancer detected at a later stage when it is more difficult to treat.
A 2017 study in the journal Clinical Gastroenterology and Hepatology found that people under 50 tended to wait two months longer to seek medical attention after first noticing symptoms than those over 50.
Amid concerns over the rising rate among younger adults, in 2021 the US Preventive Services Taskforce lowered the screening age from 50 to 45 years old.