By Gregory Seltzer, MD, Gastroenterologist—Virtua Gastroenterology

If you’re age 45 or older and you haven’t been screened for colorectal cancer, what’s stopping you?

Maybe you heard that preparing for a colonoscopy can be a bit of a hassle or you’re scared or embarrassed to have the procedure. While a colonoscopy is still the best option, there are other tests that screen for colon and rectal cancer. Here’s what you need to know about traditional colonoscopies and how they compare to non-invasive colorectal cancer screening tests.

What is a colonoscopy?

A colonoscopy is the gold standard for colorectal cancer detection and the only screening that can prevent cancer. A colonoscopy allows a doctor to examine the entire colon for cancer and precancerous polyps.

During the procedure, the doctor inserts a thin, flexible tube with a tiny camera called a colonoscope through the rectum and into the colon to look for colon polyps and cancer. Colon polyps are growths that can turn into cancer. Colon polyps can be removed during a colonoscopy and this prevents colon cancer in the future.

Colonoscopies are so effective at preventing colorectal cancer that many people only need to have one every 10 years.

What are the alternative colorectal cancer screening tests?

Alternative tests to a colonoscopy use either a stool or blood sample. There are three types of stool tests:

• Hemoccult test
• Fecal immunochemical test (FIT)
• Cologuard

The hemoccult test and FIT look for blood in the stool and need to be repeated every year.

Cologuard identifies blood in the stool and DNA mutations that can be an early indicator for colorectal cancer or advanced precancerous polyps. Cologuard is available by prescription and needs to be repeated every three years.

In July 2024, the U.S. Food and Drug Administration approved a blood test for people at average risk of colon cancer. The test, called Shield, looks for the presence of specific changes to DNA which indicate the presence of a tumor or precancerous growth in the colon.

How are these screening tests different from colonoscopies?

The screening tests above look for signs of colorectal cancer in stool or DNA, while a colonoscopy involves a visual examination of the entire colon.

The U.S. Preventive Services Task Force doesn’t play favorites when it comes to colon cancer screenings. Since one-third of Americans between the ages of 50 and 75 have never been screened, it’s best to offer choices to encourage more people to be screened.

If you’re weighing your options between a colonoscopy and an alternative screening, here are the key differences to consider:

Colonoscopy

• You must prep the bowels the day before your colonoscopy using a special laxative preparation that empties the bowels and follow a clear-liquid diet as well. This gives the doctor a clear view of the inside walls of the colon.
• A colonoscopy is a 20-to-30-minute outpatient procedure that’s done while you’re under sedation. You’ll need the day off from work and a ride home from the procedure.
• It is the only option that allows your doctor to detect and remove polyps in the earliest stage and to diagnose advanced colon polyps or colorectal cancer.
• Depending on the results of your colonoscopy, you may not need another one for 10 years.

Stool-based colon cancer screenings

• You don’t have to prep the bowels or change your diet before these tests.
• You use a special kit to collect a stool sample at home and then mail it to a lab. A hemoccult test needs samples from three bowel movements, preferably from three consecutive days. FIT and Cologuard only require one stool sample.
• Stool-based screening tests provide information as to whether there’s blood or a certain DNA mutation present in the stool that indicates colorectal cancer.
• Stool-based colon cancer screenings can have a higher false-positive rate because a benign condition like hemorrhoids can cause bleeding that’s picked up in the test.
• If these screenings detect you’re at risk for colorectal cancer, you’ll still need to have a colonoscopy so the doctor can examine the colon for polyps or cancer.
• A follow-up colonoscopy is still needed to confirm any positive findings and remove cancerous or precancerous growths.
• A hemoccult test and FIT need to be repeated yearly; Cologuard needs to be repeated every three years.

Blood-based colon cancer screening

• The screening can be added to routine blood work recommended by your health care provider.
• In a study, the test identified colorectal cancer in 83% of people later confirmed by a colonoscopy.
• The test is less sensitive in detecting precancerous polyps.
• A follow-up colonoscopy is still needed to confirm any positive findings and remove cancerous or precancerous growths.

Which screening test is right for me?

A colonoscopy is the only test that screens for and prevents colorectal cancer, so your doctor will likely recommend this procedure first. If you can’t or don’t want to have a colonoscopy, a stool-based or blood test is still an option. Just be sure to be screened if you’re age 45 or older or earlier, depending on your medical history and risk factors.

If you have concerns about having a colonoscopy, talk to your doctor. It’s normal to feel a little nervous about having a colonoscopy—especially if you’ve never had one before. Your doctor may be able to provide reassurance that puts your mind at ease or suggest some things you can do to make your colonoscopy and the prep more comfortable and convenient.

Read more about colorectal cancer screening tests and colonoscopy, or call 888-847-8823 to schedule a consultation with a Virtua physician.