How to detect colon cancer without a colonoscopy

Current screening guidelines suggest that people at average risk for colorectal cancer should get their first colonoscopy at age 45. But concerns about bowel prep, taking time off work and anesthesia during the procedure can keep some people from getting screened.

Good news: a colonoscopy is not your only option. We spoke with gastroenterologist David Richards, M.D., about alternatives to a colonoscopy and why getting screened in any way is better than skipping colorectal cancer screening altogether.

Other ways to screen for colon cancer

A colonoscopy is the gold standard test in the United States for colon cancer screening because it can detect cancer as well as prevent cancer by finding and removing precancerous polyps. But there are other screening options available for people at average risk.

Stool-based tests

If you choose a stool-based test, UT MD Anderson recommends you start getting tested at age 45.

Fecal immunochemical test (FIT)

A FIT is an inexpensive, at-home test that looks for proteins found in your blood. Blood in your stool could be a sign of colon cancer. If your FIT result is positive, you will need to get a colonoscopy. If you choose FIT screening instead of a colonoscopy, it’s recommended to get tested every year.

Stool DNA or RNA test

This at-home test combines FIT with testing for DNA and RNA mutations in your stool that happen as colon cancer develops. A positive result means you’ll need to get a colonoscopy. This test is typically recommended every three years.

“Stool-based tests are pretty good at detecting colon cancer, but not as good at detecting precancerous polyps,” says Richards. “Early cancer detection is important, and if we can find and remove precancerous lesions before they become cancer, that’s even better.”

Virtual colonoscopy

A virtual colonoscopy uses a CT scan and specialized software to create detailed images of your colon. A radiologist will look at these images to check for polyps or other abnormalities.

Virtual colonoscopies require the same bowel prep as a colonoscopy, and if your doctor finds anything during the virtual colonoscopy, you’ll need a diagnostic colonoscopy to diagnose the issue.

If you’re at average risk for colon cancer, UT MD Anderson recommends that you get your first virtual colonoscopy at age 45 and every five years after that if your results are normal.

Not all insurance providers will cover the cost of a virtual colonoscopy, so check with your insurance provider before scheduling this test. 

Sigmoidoscopy

A sigmoidoscopy – sometimes called a flexible sigmoidoscopy or flex sig – is a procedure that allows doctors to examine the inside of the rectum and sigmoid colon (the lowest part of your colon).

Doctors can remove precancerous polyps during a sigmoidoscopy. It requires less bowel prep than a colonoscopy, and you may not be sedated or given anesthesia before the procedure. However, a sigmoidoscopy is not as good as a colonoscopy in detecting cancer or precancerous polyps higher up in the colon. So, it’s not as widely used in colorectal cancer screening. If your doctor finds something suspicious during a sigmoidoscopy, you will need a colonoscopy.

A sigmoidoscopy is recommended every five years or every 10 years with a FIT every year. 

Blood tests

Blood-based tests look for DNA changes in your blood that may indicate cancer. They may appeal to people who are at average risk for colorectal cancer and are not willing or able to use other colorectal cancer screening tests.

Blood tests for colorectal cancer screening must be prescribed by your doctor.

They are currently recommended every three years. However, they are not as effective as colonoscopies or most stool-based tests for detecting stage 1 colorectal cancer or precancerous polyps.

“Still, if more patients are able or willing to get screened with blood tests, that is certainly better than no screening at all,” says Richards.

If your blood test results come back positive, you will need a diagnostic colonoscopy so your doctor can examine your entire colon and check for any issues.

Remember: these screening options are for people at average risk for colorectal cancer. If you are at increased or high risk, you will need to be screened by colonoscopy. You will also need to start screening at an earlier age and be tested more often. Talk to your doctor about a personalized screening plan.

Know the warning signs of colon cancer

Screening is essential, but it’s also important to recognize possible symptoms of colon cancer. Colorectal cancer rates are rising among young adults, so everyone should be aware of the warning signs, regardless of age.

Colon cancer symptoms may include:

• Blood in the stool or toilet after a bowel movement
• Abdominal pain or cramping
• Changes in bowel habits, such as the size, shape or frequency
• Diarrhea or constipation that does not go away
• Bloating or feeling full
• Extreme fatigue
• Unexplained weight loss

Colon cancer doesn’t always cause symptoms, especially in its early stages. That’s why routine screening is so important. It can help detect cancer early, when it’s most treatable, and your doctor can look for and remove precancerous polyps before you show symptoms.

The bottom line: Get screened

“There is still work to be done among younger adults ages 45 to 49 because less than half of those who are eligible actually get screened for colon cancer,” says Richards.

Screening is especially important for Black men and women, who have the highest rate of colon cancer among all races in the United States.

Whichever test you choose, the most important thing is to get screened.

“Colorectal cancer screening saves lives, and we have multiple options for screening,” says Richards. “The best test is the one that you’ll follow through with.”

Request an appointment at UT MD Anderson online or call 1-877-632-6789.