Colorectal cancer is the second leading cause of cancer deaths in the US, but its target population is changing.
While rates have steadily decreased for more than a decade in adults over 65, cases among another population are suddenly exploding.
Now, scientists are racing to understand why this shift is happening — and why these new cases are so aggressive.
You may have seen that colorectal cancer is rising among people younger than 50.
However, new research reveals that this increase is most dramatic among a younger population within that group: kids aged 10 to young adults in their early 20s.
In fact, one study shows that the younger the group, the more stark the increase: colorectal cancer (CRC) surged a shocking six-fold in kids aged 10 to 14 from 1999 to 2020.
The disease more than quadrupled among teens 15 to 19, and almost doubled in young adults aged 20 to 24 during the same time period.
Another study showed that during that time frame, CRC incidence was relatively stable from 1999 to 2012. Then, incidence among children ages 10 to 14 began climbing at an estimated 70.54% annually from 2012 to 2015 — a rate that compounds to a nearly 400% increase over those three years.
But rising cases are only part of why these colorectal cancer trends are so troubling.
Why colorectal cancer appears differently in younger patients
Experts are concerned not only about the rising rates, but about how different the CRC behaves when younger folks develop the disease.
When cancer is found in younger patients, a majority of cases are advanced, aggressive cancers: Stage 3 or 4, new research shows. And these younger patients are more likely to have worse outcomes — after treatment, their cancer is more likely to return, another paper suggests.
“We do feel like it is a bit of a distinct disease than what we’re seeing in older adults,” pediatric surgeon Dr. Erica Arnold told Live Science.
Arnold led research studying young CRC patients, finding that patients were diagnosed quickly after getting their first symptoms — about 12 weeks.
The findings support that conclusion, showing that despite treatment, cancer returned in 37% of patients. By the end of that study, 45% of CRC patients died from the disease.
“Some of that might be related to delays in diagnosis,” gastrointestinal oncologist Dr. Christopher Lieu told Live Science. “but if you want my honest opinion, it does suggest that these cancers are developing differently.”
What’s causing these changing trends
Experts still don’t know what’s behind these changes. But they suspect that lifestyle factors such as eating ultra-processed foods, lack of exercise and obesity are big factors in why CRC is rising in such young populations.
This can play into imbalances in the gut microbiome, which is the subject of “most of the research” teasing out a cause, Lieu said. These factors can cause long-term inflammation, which can trigger mutations that lead to cancer.
Plus, there’s the question of whether antibiotics mess with the delicate balance in the GI system. Other researchers believe that increasing ingestion of microplastics might be disrupting the mucus lining of the bowel tract.
“It may be a combination of food, antibiotic use and environmental exposures,” Lieu said.
What to look out for
Though rates are rising, colorectal cancer is still very rare among people younger than 20, with one case in every 200,000 people each year. Fewer than 100 cases are diagnosed in children each year in the US.
That said, it’s important to know the signs when younger populations aren’t going through routine colonoscopies to check for problems, like those over 45.
There’s one symptom that’s the strongest predictor of CRC in folks under 50: Rectal bleeding.
“If they’re 35 and they come in with rectal pain, they probably don’t need a colonoscopy,” said Dr. Sandra Kavalukas, a colorectal surgeon at the University of Louisville School of Medicine. “But if they come in with a bleeding complaint, they are 8.5 times more likely to have a colorectal cancer.”
In Arnold’s study, the most common symptoms were back and abdominal pain (74%), change in bowel habits (45.2%), weight loss (43%) and rectal bleeding (38%).
“If you have a person below the screening age with rectal bleeding, you should seriously consider a colonoscopy,” Kavalukas stressed.
