Gastrointestinal cancers, which include colorectal, stomach and pancreatic cancer, are rising dramatically in younger adults, though doctors aren’t fully sure why. Even some of the possible causes require more research, they say.
According to a review published Thursday in JAMA, gastrointestinal cancers have become the fastest-growing type of cancers diagnosed in adults younger than 50 in the U.S.
The review, one of the most comprehensive looks at gastrointestinal cancer trends, summarized the findings of major international and U.S. cancer databases, plus 115 papers on gastrointestinal cancers published from January 2014 to March 2025.
The authors underscore the need for people to follow the screening guidelines for colorectal cancer, which suggest that people with an average risk start screening — usually a colonoscopy or stool test — at age 45. Since doctors don’t routinely screen for pancreatic, stomach and esophageal cancers in the U.S., the authors also call for new ways to screen more people for these cancers.
“This really points to the importance of trying to improve screening and early detection,” said Dr. Kimmie Ng, the review’s co-author and director of the Young-Onset Colorectal Cancer Center at Dana-Farber Cancer Institute.
According to the review, colorectal cancer is by far the most common early-onset gastrointestinal cancer, with nearly 185,000 cases reported worldwide in 2022 and nearly 21,000 cases reported that same year in the U.S. Diagnoses in the U.S. have risen 2% annually in people younger than 50 since 2011, according to the American Cancer Society.
“It never used to happen in this age group, and now a very significant rise in 20-, 30- and 40-year-olds are getting colon cancer,” said Dr. John Marshall, chief medical consultant at the nonprofit Colorectal Cancer Alliance, who was not involved in the research. In one of the most high-profile examples, actor Chadwick Boseman was diagnosed with colon cancer in 2016 and died of the disease four years later at age 43.
Early-onset cases of pancreatic, stomach and esophageal cancers are also rising, according to the new study. Previous research has shown a disproportionate share of those gastrointestinal cancer diagnoses were among Black and Hispanic people. Pancreatic cancer is among the deadliest forms of cancer, with just 13% of patients surviving five years after their diagnosis.
Because colorectal cancer is the most common, doctors said they have a better grasp of what might be contributing to these early-onset cases compared with others.
“If we can understand what’s going on in colorectal [cancer], I think it would really provide a lot of guidance to help us understand the other GI tract cancers,” said Dr. Scott Kopetz, a professor of gastrointestinal medical oncology at the University of Texas MD Anderson Cancer Center.
Kopetz said there are likely multiple factors driving the increase in early-onset cases.
“The leading theory is that there is no single leading theory,” he said.
Ng’s new review in JAMA suggests that most gastrointestinal cancers in people under 50 are associated with lifestyle factors such as obesity, lack of exercise, poor diet, cigarette smoking or alcohol consumption. One study included in the review found that women who consumed more sugar-sweetened beverages during adolescence had a higher risk of developing early-onset colorectal cancer.
“It’s really what people were doing or exposed to when they were infants, children, adolescents that is probably contributing to their risk of developing cancer as a young adult,” Ng said.
Health Secretary Robert F. Kennedy Jr. has been vocal about the association between sugary beverages and health issues, including cancer. On Wednesday, President Donald Trump said Coca-Cola will start being made with cane sugar rather than corn syrup in the U.S., but the company did not commit to the change when asked about it by NBC News.
Marshall said he suspects the rise in early-onset colorectal cancer could have something to do with changes in people’s gut microbiomes — the bacteria that live in our gastrointestinal tracts. Diet, antibiotic use, microplastics and exposure to environmental chemicals likely all influence a person’s gut bacteria, but scientists still don’t have a clear understanding of what a healthy microbiome looks like nor how it affects our health. That is a booming area of research.
Ng’s review also found that 15% to 30% of people with early-onset gastrointestinal cancer carry hereditary genetic mutations that may have predisposed them to getting cancer at a young age. Because of that, she said, “we do recommend that all young patients diagnosed under the age of 50 undergo testing for hereditary conditions.”
Overall survival rates for gastrointestinal cancers have gotten better over time, due to improvements in treatment and screening. But Ng’s review found that younger patients often have worse outcomes, despite typically receiving more treatments, including more surgery, radiation and aggressive combinations of chemotherapy, she said.
One reason could be that primary care doctors may overlook symptoms such as abdominal pain, constipation, heartburn or reflux in younger patients, thereby delaying their diagnoses.
“My personal feeling is that it’s because we’re finding them at a more advanced stage, because people don’t really think of colon or other GI cancers when they see a young person with these nonspecific complaints,” said Dr. Howard Hochster, director of gastrointestinal oncology at Rutgers Cancer Institute and RWJBarnabas Health in New Jersey.
But Ng said that even after controlling for the stage at which patients are diagnosed, young people still seem to have worse survival rates.
“This makes us wonder as researchers whether that means that the cancers that develop in younger people may be biologically different and more aggressive, or maybe less responsive to treatment,” she said.
