Which Colon Cancer Test Is Right For You?

The colonoscopy is the best-known screening test for colon cancer, but there are other options you may want to consider.

Which Colon Cancer Test Is Right For You?

Medically reviewed in September 2020

Updated on December 1, 2020

Colorectal cancer, which can include either colon cancer or rectal cancer, is the second leading cause of cancer-related deaths in the United States. Yet, according to the American Cancer Society (ACS), about half of colon cancer deaths could be prevented with early screening.

Why aren’t more people taking advantage of these tests?

By and large, they’re fairly simple and painless procedures. But the preparation required for some colon cancer tests has given them bad reputations. Typically, that involves drinking a strong laxative beverage the day before to flush out your bowels—which means close proximity to a bathroom is an absolute must. Painful? No. Unpleasant? Yes.

Other types of tests have their pros and cons. But a day or two of discomfort is a small price to pay for a screening that can detect suspicious polyps or tumors that may be pre-cancerous or cancerous. And when it comes to cancer of any kind, treatment is often most successful when found early.

When to start screenings
The American Cancer Society recommends that men and women be screened for colon cancer starting at age 45. If you are at increased or high risk—including having had colon cancer or polyps in the past, a history of inflammatory bowel disease or a family history of colon cancer—you should get screened earlier. Discuss these and other risk factors with your doctor to help decide when to start screening.

Also discuss lifestyle changes you might be able to make to lower your risk of colorectal cancer. These include managing your diet, getting more physical activity and reducing your alcohol intake. If you smoke, seek help to try to quit.

Preventive screening options
The colonoscopy is still considered the gold standard for detecting colon cancer, but there are several other options worth discussing with your doctor. Here’s what you should know about each one:

Frequency: Once every 10 years

Preparation: As with all colon-screening tests (except for the at-home variety), your doctor needs a clear view of your colon—and that means it needs to be clean and empty. Your doctor will provide you with detailed instructions on how to prepare. One of the most common ways involves drinking 2 to 4 quarts of a liquid laxative the night before and morning of the procedure. You’ll also be asked to stop eating food and drink only clear liquids at least one day before the test. If you take any medications, talk with your doctor ahead of time about how to manage them prior to the procedure.

About the test: A colonoscopy is a routine procedure that can be done at a doctor’s office, clinic or hospital outpatient department. It usually lasts from 30 minutes to an hour. To minimize discomfort, you’ll first receive a sedative through an IV or by taking a pill. To begin, your doctor inserts a colonoscope—a thin tube with a small video camera on the end—through your rectum and into your colon, providing a full view of all five feet of it. One advantage to this type of screening is that if polyps are found, your doctor can remove them right then and there. If a polyp is removed, it’s sent to a lab to check for signs of cancer. If your doctor sees any other abnormality, such as a tumor or larger polyp, they will likely take a tissue sample (biopsy) for further examination.

After the test: Because the sedative will make you groggy, you’ll be asked to arrange for someone to drive you home. You may also feel bloated, gassy or have cramps for the rest of the day.

CT colonography (virtual colonoscopy)
Frequency: Once every five years

Preparation: Much like a colonoscopy, you’ll need to empty your colon by drinking a salty liquid laxative solution the night before and morning of the screening. Again, a bathroom is your best friend as you prepare. You’ll also be asked to follow a clear liquid diet a day or two before the procedure.

About the test: The “virtual” colonoscopy only takes about 10 minutes. It doesn’t require sedation and is done in a facility with a CT scanner. (If you’ve ever had a CT scan, you’ll be familiar with how it works.) To begin, you’ll be positioned on the scanner table so that a small, flexible tube can be placed into the rectum. Air is then pumped inside the tube to inflate the colon, offering a clearer view of the area tested. The table then slides into the scanning machine and a special computer program takes images of the colon, generating two-dimensional X-rays along with a three-dimensional view. The first scan is taken while lying on your back; a second is taken while on your stomach. The X-ray images are later examined for polyps and cancer. While this procedure is less invasive than a regular colonoscopy, one of the drawbacks is that if your doctor finds any abnormalities, you’ll probably need a colonoscopy. This test may not be covered by your insurance.

After the test: You may feel bloated or crampy.

Flexible sigmoidoscopy
Frequency: Once every five years

Preparation: A clear liquid diet the day before the exam may be required and you’ll need to drink a strong laxative. An enema may also be needed to be sure all waste is eliminated.

About the test: This procedure only takes 10 to 20 minutes and can be done without sedation. During a flexible sigmoidoscopy, your doctor inserts a thin, flexible, lighted tube with a video camera on the end through the rectum and into the lower part of the colon. Because the sigmoidoscope is only about two feet long, your doctor is only able to see a portion of the colon. If any abnormalities are detected, your doctor may take a tissue sample for further examination. You’ll also need to have a colonoscopy for examination of the rest of your colon.

Fecal occult blood test (FOBT) or fecal immunochemical test (FIT)
Frequency: Once every year

Preparation for a FOBT: Your doctor may ask you to avoid taking nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen, naproxen or aspirin a week before testing. You may also be asked to limit taking vitamin C and eating red meat for three days prior.

About the FOBT: This screening test is different from a colonoscopy or sigmoidoscopy because it can be done in the privacy of your own home. It relies on sending stool samples to your doctor’s office or a lab for testing. (Don’t worry, you’ll only need to send a thin film of stool smeared onto special cards). Detailed instructions on how to get the samples and return them are provided in a special kit. If blood is found in the stool by way of a chemical reaction in the lab, you’ll need a colonoscopy to determine the cause of the bleeding.

Preparation for a FIT: Unlike the FOBT, there are no drug or dietary restrictions.

About the FITYou’ll receive a test kit with detailed instructions for collecting and mailing stool samples to your doctor’s lab. If the test shows hidden blood in your stool (in other words, you don’t see blood when you have a bowel movement), you’ll need a colonoscopy.

Stool DNA test
Frequency: Once every three years

Preparation: No special preparation is required.

About the test: This screening test, which also requires stool samples, looks for abnormal DNA that would appear in polyps or cancerous cells. You’ll again receive a kit for collecting and delivering stool samples and a colonoscopy will be necessary if the results show any abnormalities.

Which test is right for you?
There isn’t a one-size-fits-all approach to colon cancer screening. Each test has its advantages and disadvantages. Your risk level for colon cancer is an important factor in determining the best test for you. The stool-based and X-ray tests are more likely to produce false-positive results. (A false positive suggests that an abnormality is present when it really is not.) The direct visualization tests (like the colonoscopy) are more invasive and some cause more discomfort than others. That’s why it’s important to talk to your doctor about the pros and cons of each option.

Regardless of which test you choose, early detection increases your chance for successful treatment if colon cancer is found. If you’re at least 45 years old or at increased risk for colon cancer, speak with your doctor today.


National Institute of Diabetes and Digestive and Kidney Diseases. "Flexible Sigmoidoscopy." Published July 2016.
American Cancer Society. "Colorectal Cancer Prevention." Published September 6, 2020.
American Cancer Society. "Colorectal Cancer Guideline: How Often to Have Screening Tests." Published June 29, 2020.
Centers for Disease Control and Prevention. "What Should I Know About Screening for Colorectal Cancer?" Published February 10, 2020.

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