Why is colon cancer on the rise in young adults?

March is Colon Cancer Awareness Month, and doctors and health advocates are sounding the alarm on a disturbing trend: More younger Americans are getting diagnosed with the disease. What’s more troubling is that many of the cases are at an advanced stage, perplexing doctors.

The colon and the rectum are part of the large intestine. Colon cancer, formally known as colorectal cancer (CRC), typically begins when a mutation occurs, leading to abnormal cell growth. This can result in the formation of colon polyps, which the Mayo Clinic defines as small clumps of cells that form on the lining of the colon. In the early stages these polyps can be benign, but over time they can become cancerous. This type of cancer has been known to mostly affect older adults, but it’s increasingly being seen in younger people around the globe.

The alarming increase in colon cancer diagnoses among young people was highlighted in a recent American Cancer Society report. According to the research, in Americans younger than 55, rates have nearly doubled, from 11% in 1995 to 20% in 2019. Some studies estimate that the disease could become the leading cause of cancer deaths in the U.S. for people ages 20-49 by the year 2040.

But what’s even more concerning to doctors is that advanced-stage diagnoses among young patients are also climbing significantly. According to the report, “60% of all new cases were advanced in 2019 versus 52% in the mid-2000s.”

To better understand why this is happening, Yahoo News spoke to Dr. Marios Giannakis, a medical oncologist and clinical investigator at the Young-Onset Colorectal Cancer Center, which is part of Dana-Farber Cancer Institute​​ in Boston. The center provides care for patients with early-onset colon cancer and also conducts multidisciplinary research to better understand the disease, as well as to develop ways to prevent, detect and treat it.

Why is colon cancer in young people on the rise?

“This epidemic of young-onset colorectal cancer is still fairly recent and still largely unexplained,” Giannakis told Yahoo News.

He explained that early-onset CRC has some unique characteristics. It tends to be more aggressive and often presents on the left side of the colon rather than the right, and some patients with this type of cancer experience abdominal pain or rectal bleeding. However, he noted that many patients may not exhibit any symptoms.

Why CRC cases among people younger than 50 are on the rise is a puzzling question that remains unanswered, and one, Giannakis said, that underscores the need for ongoing research. But there are some clues as to why this may be happening.

Experts believe lifestyle risk factors could be contributing to the uptick in rates of early-onset CRC. Younger Americans are experiencing higher rates of obesity and are leading more sedentary lives. They are also consuming higher amounts of processed and sugary foods, according to experts. All of these factors are known to increase the risk of developing colon cancer.

According to the American Cancer Society, 55% of all CRCs are linked to lifestyle factors. However, the organization notes that the strongest risk factor for developing the disease is having a family history of it.

Environmental exposures have also been associated with young-onset CRC, Giannakis said.

“One of the thoughts following the epidemiologic trends of this phenomenon happening really since the ’90s ... is what’s called the birth cohort effect,” he said. “That essentially means that some risk factor or maybe a combination of risk factors in the environment just carried forward in younger generations because younger generations are just more exposed to it,” he added.

But Giannakis said lifestyle and environmental factors don’t tell the whole story.

“Could be other things that we don’t quite understand pertaining to the molecular types of cancers, the cancers themselves, but also the microenvironment of the cancer, [or] what surrounds these early-onset tumors,” he said.

Studying the microbiome — a community of microorganisms, mainly bacteria, that are found throughout the human body, particularly in the gut — is one of the areas of research that Giannakis’s team is focusing on. He said one question they hope to answer is “if the microbiome in our guts is changing in a way that facilitates colon cancer.”

According to Dana-Farber Cancer Institute, recent studies have found that these bacteria may play a role in how CRCs develop and also in how they respond to treatments.

In a new paper published in Science, co-authored by Giannakis, Dana-Farber Cancer Institute researchers outlined the type of studies that are needed to better understand the underlying causes and biology of young-onset CRC. This research, the authors noted, should look at a combination of things such as genetics, environmental and lifestyle factors, people’s immune systems and the environment in which these cancers grow.

Where in the U.S. are more younger people being diagnosed with colon cancer?

A recent Cleveland Clinic study provides some insight into where young-onset CRC cases and deaths seem to be more prevalent in the U.S.

“Among the youngest patients, we found notable hot spots in the Midwest and also the Great Lakes region,” Blake Buchalter, a researcher for Cleveland Clinic and lead author of the study, said in a statement. In addition to finding these hot spots, the team of researchers located three places where young-onset colon cancer is less common: the Southwest, California and the Mountain West region.

Researchers said it is unclear why colon cancer among young people is more common in certain areas of the country, but they plan to investigate further to find some answers.

But we do know who in the population is at higher risk. Based on new data from the American Cancer Society, three groups in the U.S. population — American Indians, Alaska Natives and Black Americans — are disproportionately affected by the disease, having the highest rate of both diagnoses and deaths of all groups in the country.

How can people lower their risk of colon cancer?

The Centers for Disease Control and Prevention says the most effective way to reduce a person’s risk of colon cancer is to get screened routinely. The age that an average-risk person should get screened was lowered in 2021 from 50 to 45. However, some individuals, such as those with a family history of CRC and Black Americans, should consider doing it earlier. The American College of Physicians recommends that Black men and women undergo their first screening at age 40.

The gold standard for colon cancer screening, Giannakis said, is a colonoscopy. The test can visualize where polyps are located in the colon, and doctors can remove most of these and some cancers during the procedure. However, most people younger than 45 are not eligible for colonoscopies, so experts believe that lowering the screening age in the future may be necessary to be able to catch cancers in people in their 20s or 30s.

Besides a colonoscopy, there are other types of screening tests available in the U.S. The CDC recommends consulting with a doctor to determine which one is best for you.

To lower your risk of developing CRC, the agency recommends eating a healthy diet “low in animal fats and high in fruits, vegetables, and whole grains.” Increasing physical activity, keeping a healthy weight, as well as reducing alcohol consumption and smoking can also reduce a person’s risk of developing this type of cancer.

Finally, Giannakis said young people should not be ignoring symptoms associated with the disease. These can include changes in bowel habits, blood in the stool, abdominal pain and weight loss.

“It’s important to listen to our bodies when symptoms that are suggestive of cancer appear even at younger ages. However, realizing that a lot of these cancers are asymptomatic, we should really be faithful to screening as well and pursue that,” he said.