Colon cancer deaths among young people are expected to have doubled in two decades by 2030, experts warn.
The cancer – which is especially hard to treat due to late diagnosis and broad symptoms – is also expected to become the number one cause of cancer deaths in people under 50 by the end of the decade.
Doctors are still trying to work out what’s behind the unprecedented rise, but theories include modern diets, antibiotic use, and even fungus.
Dr Christopher Lieu, co-director of gastrointestinal medical oncology at University of Colorado Medicine, said: ‘Colorectal cancer will be the number one cause of cancer-related deaths in [patients] 20 to 49.’
Speaking at a cancer conference in Chicago on Saturday, he added: ‘This is a humongous issue.’
Data from JAMA Surgery, which Dr Lieu referenced in his presentation this weekend, showed that colon cancer is expected to rise by 90 percent in people ages 20 to 34
The same data shows that rectal cancer will rise by 124 percent in the youngest age group
Cancers of the colon and rectum are currently the third most common type in the US and the third leading cause of death of both men and women.
Dr Lieu said that in young people, both diagnoses and death rates are climbing, even though rates in older populations are declining.
The American Cancer Society estimates about 153,000 colorectal cancer cases will be detected this year, including 19,500 among those under 50 years old.
Some 52,550 people are expected to die from the disease.
In a March report from the ACS, scientists warned that the rate of colon cancer in people aged 50 to 54 nationwide was now nearly 60 per 100,000.
For comparison, between 1975 to 1979 the rate was around 40 per 100,000 – indicating a 50 percent increase in around 45 years.
About 43 percent of diagnoses were in people aged 45 to 49 years old.
The US is not the only country seeing these alarming rates. A 2023 review found that while the US had an early-onset colorectal cancer rate of 12.4 per 100,000 people, Australia had 13.5, Norway had 10.5, Korea had 10.1, and the United Kingdom had 9.3.
‘We don’t know why this trend is being seen in numerous countries that have different diets and exposures and environmental factors,’ Dr Lieu said.
A 2020 survey from Colorectal Cancer Alliance found that many patients with colorectal cancer symptoms were initially misdiagnosed or dismissed
Dr Lieu said that based on data from JAMA Surgery, between 2010 and 2030, colon cancer will have increased by 90 percent in people ages 20 to 34. In the same age group, rectal cancer will have spiked by 124 percent.
Experts have commonly blamed unhealthy diets, alcohol consumption, and sedentary lifestyles on this shift, though some research suggests otherwise.
A 2021 study, for example, found that early-onset cancer patients were less likely to be obese or be smokers than their older counterparts.
Dr Lieu pointed to health impacts and exposures that young-onset colorectal cancer patients have had as early as birth.
Dr Christopher Lieu of the University of Colorado Medicine said that the rise of colon cancer in young people is ‘a humongous problem’
A study published in April examined how being born via c-section influenced the chance of developing early-onset colorectal cancer. The researchers found that females born via c-section were more likely to develop colorectal cancer earlier in life than those born vaginally. There was no association among males.
Additionally, antibiotic use has been shown to impact this risk. One study in journal Gut found that prolonged antibiotic use resulted in increased risk of early-onset colon cancer. However, it was also associated with a lower risk of rectal cancer.
And research presented at the American Society of Clinical Oncology’s annual meeting this weekend showed that the fungus Cladosporium sp. was more common in the tumors of young patients than the older individuals.
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.
These environmental factors have a lasting impact on the gut microbiome, which experts think could increase the risk of colorectal cancer, even when exposure was limited to early life.
‘People are carrying this increased risk with them as they age,’ Dr Lieu said.
Part of what makes colorectal cancer difficult to diagnose is its symptoms, which can often be attributed to other conditions. However, some stand out more than others.
A study published last month in the Journal of the National Cancer Institute found that the most reported symptoms were abdominal pain, blood in the stool, diarrhea, and iron-deficiency anemia.
Additionally, in a 2020 survey by Colorectal Cancer Alliance, 68 percent of participants said they experienced blood in their stool. The average participant age was 42.
‘This is a concerning finding and something that should never be taken lightly, especially by primary care providers,’ Dr Lieu said.
The same survey also found that many patients with colorectal cancer symptoms were initially misdiagnosed or dismissed.
More than half of respondents said they were misdiagnosed with conditions such as hemorrhoids, irritable bowel syndrome, anemia, and mental health issues. And patients ages 19 to 39 were more likely to feel dismissed by their provider.
In one study, with just one symptom took an average of 10 months to receive a colorectal cancer diagnosis. Those with at least three symptoms were diagnosed after five months on average.
‘Five months is still way too long to be diagnosed with obviously a very deadly disease,’ Dr Lieu said.
Spending longer amounts of time without a diagnosis could allow colorectal cancer to advance to later stages, making it more difficult to treat.
‘Some of our stage IV patients were waiting more than a year to be diagnosed from the onset of their symptoms,’ Dr Lieu said. ‘We should not be surprised when they show up with later stages of disease.’
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.
This is usually a colonoscopy, where a camera is inserted into a person’s rectum, searching for growths or changes to their intestines.
However, patients younger than 45 are less likely to get screened since they don’t fall within the recommended age range.
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.
In a 2019 study, 63 percent of colorectal cancer patients didn’t even know that this type of cancer could occur in people under the age of 50.
Dr Lieu said in a call to action that educating physicians and patients on what signs to look out for and expanding risk assessments and genetic testing could help researchers better understand what is causing this increase.
‘Awareness is key,’ he said.