You’re at risk of colorectal cancer. Know the symptoms. Get screened.

By Nicole Brudos Ferrara

Colorectal cancer is no longer a disease of older people. People in their 50s, 40s and younger are increasingly being diagnosed with cancers of the colon and rectum. Incidence rates increased by about 2% per year in people younger than 50 during the past decade, according to the American Cancer Society. In 2019, 20% of colorectal cancers were in people ages 54 years or younger, up from 11% in 1995.

Another trend: Rectal cancer is more common than colon cancer in younger people. Of the estimated 46,050 new cases of rectal cancer in 2023, 37% will be in people younger than 50 versus 24% in people 65 or older.

Because of these trends, experts now recommend screening for colorectal cancer at age 45. But Derek Ebner, M.D., a Mayo Clinic Comprehensive Cancer Center gastroenterologist, says adults of all ages should be aware of the symptoms of colon and rectal cancer and report them to a healthcare professional.

"When we detect cancer early, and it's still confined to the colon or the rectum, that five-year survival is wonderful — it's 90% or better. Detecting cancer later, when it's had an opportunity to move beyond the colon or the rectum, the five-year survival is much lower — typically 15% or less," says Dr. Ebner.

Here's what you need to know to prevent colorectal cancer or catch it early when it's most treatable:

Everyone is at average or high risk of colorectal cancer.

"The truth is everyone's at risk for colorectal cancer," says Dr. Ebner. "But we typically divide people into two groups, those who are average risk and those who are high risk."

People at average risk of colorectal cancer might not experience symptoms associated with the disease and don't have any known factors that make them high risk.

"For those at high risk, there tends to be at least one of three variables: A medical condition, a genetic condition, or a family history that places them at higher risk," says Dr. Ebner.

Medical conditions that increase the risk of colorectal cancer include a personal history of colorectal cancer or polyps, inflammatory bowel disease, diabetes and obesity.

Genetic conditions that increase the risk of colorectal cancer include familial adenomatous polyposis and Lynch syndrome. Familial adenomatous polyposis (FAP) is a rare condition caused by a defect in the adenomatous polyposis coli (APC) gene. While most people inherit the gene from a parent, the genetic mutation occurs spontaneously in 25% to 30% of people with FAP. Lynch syndrome is a condition that increases the risk of many kinds of cancer, including colon and endometrial cancer, and it is passed from parents to children.

Family history associated with a higher risk of colorectal cancer involves a first-degree family member — a parent or sibling — with a colorectal cancer diagnosis or precancerous polyps. If you have a family history, you must start screening sooner and perhaps more often than people at average risk.

Dr. Ebner says healthcare professionals don't yet know the reason for the increased rate of colorectal cancer among younger people, but suspect environmental factors are involved. "Over the last 50 years, we've had major changes in diet — ultraprocessed food, higher quantities of red meats," he says. "These changes have perhaps led to changes in gut bacteria. Our gut microbiome might not be as protective as it once was. We also question the role of less exercise and increasing obesity rates."

Dr. Ebner encourages everyone to reduce their risk of colorectal cancer by eating a more plant-based diet and exercising regularly.

Non-invasive screening options exist, but you may be unable to avoid a colonoscopy forever.

Most colorectal polyps do not cause symptoms, so you may have polyps without knowing it. This is why beginning colorectal cancer screening at the recommended age of 45 is critical.

Screening reduces the risk of cancer by identifying polyps in the colon and rectum that could develop into cancer. You may need to begin screening younger than 45 if you have risk factors. Ask your healthcare professional when you should start screening.

Dr. Ebner says it's impossible to overemphasize the importance of screening. "If we're able to identify polyps, we have the opportunity to remove them and prevent the development of cancer. If we diagnose cancer, unfortunately, we've missed that opportunity," he says.

In the U.S., colonoscopy is the most common screening method. A long, flexible tube (colonoscope) is inserted into the rectum during a colonoscopy. A tiny video camera at the tip of the tube allows a healthcare professional to look for changes — such as swollen, irritated tissues, polyps or cancer — in the colon and the rectum. The professional can also remove polyps or other types of abnormal tissue through the scope during a colonoscopy. Sedation or anesthesia is usually recommended.

A non-invasive option for colorectal cancer screening is a stool DNA test (offered under the brand name Cologuard), which uses a stool sample to look for signs of colon cancer. The test checks for changes in cells' DNA. Certain DNA changes indicate that cancer is present or might develop. The test also looks for hidden blood in the stool.

"If the result of a stool DNA test or another non-invasive test is positive, it's critical to follow up with a colonoscopy," says Dr. Ebner.

Watch this video to hear Mayo Clinic colorectal cancer experts explain what's involved in a colonoscopy procedure and why they get screened:

Know the symptoms of colorectal cancer, and don't wait to talk to a healthcare professional if you experience them.

The symptoms of colon and rectal cancer can include:

• A change in bowel habits, such as diarrhea, constipation or more frequent bowel movements.
• Rectal bleeding or blood in the stool.
• Narrow stool.
• Ongoing discomfort in the belly area, such as cramps, gas or pain.
• A feeling that the bowel doesn't empty.
• Weakness or fatigue.
• Losing weight without trying.

People younger than 50 who develop colorectal cancer seem to experience slightly different symptoms than older people diagnosed with the disease, says Dr. Ebner. "We still see abdominal pain and blood after bowel movements, but the change in bowel habits is more often diarrhea," he says.

A recent study of people diagnosed with early-onset colorectal cancer confirms this. Study participants experienced four warning signs in the period of three months to two years before their diagnosis:

• Abdominal pain
• Rectal bleeding
• Diarrhea
• Iron deficiency anemia

"Blood loss after a bowel movement can lead to iron deficiency anemia," says Dr. Ebner. "But sometimes that blood loss is slow or small, so you may not see it. If we see a sign of iron deficiency on a blood test, that will prompt us to explore further."

If you notice any of these symptoms, contact your healthcare professional. "These symptoms can be embarrassing, but I can't stress enough — if you have any of them, share them with a healthcare professional. We see folks experiencing these symptoms for months, sometimes up to a year," Dr. Ebner says. "Any delay in sharing this information translates to a delay in diagnosis, which can lead to later-stage cancer, and later-stage cancers can be more challenging to treat and have lower five-year survival rates. Don't delay. Make an appointment."

Learn more

Learn more about colon cancer and find a clinical trial at Mayo Clinic.

Learn more about rectal cancer and find a clinical trial at Mayo Clinic.

Join the Colorectal Support Group on Mayo Clinic Connect, an online community moderated by Mayo Clinic for patients and caregivers.

Also, read these articles:

• Colon cancer screening: Weighing the options
• Are colon and rectal cancers treated differently?
• Dear Mayo Clinic: Treating colon cancer
• Colorectal cancer in the liver: New treatment gives more people hope for a cure
• Colorectal cancer myths and facts
• Answers to 4 questions about colorectal cancer treatment and survivorship
• Plant power: Using diet to lower cancer risk