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Colorectal Cancer Screening

Colorectal cancer starts in cells that form the colon or rectum. It's one of the leading causes of cancer deaths in the U.S. But when this cancer is found and treated early, when it's still small and hasn't spread, the chances of a full recovery are very good. Because colorectal cancer rarely causes symptoms in its early stages, screening for the disease is important. Screening is even more important if you have risk factors for this cancer. Learn more about colorectal cancer, its risk factors, and screening options. Then talk with your healthcare provider to decide what's best for you.

Cross section of sigmoid colon, rectum, and anus showing cancer and polyp.

Risk factors for colorectal cancer

Your risk of having colorectal cancer increases if you:

  • Are 50 years of age or older, but it can start in people younger than 50

  • Have a family history or personal history of colorectal cancer or polyps

  • Are African American or of Eastern European Jewish descent (Ashkenazic)

  • Have type 2 diabetes, Crohn’s disease, or ulcerative colitis

  • Have an inherited genetic syndrome like Lynch syndrome (HNPCC) or familial adenomatous polyposis (FAP)

  • Are overweight

  • Are not physically active

  • Smoke

  • Drink a lot of alcohol (more than 2 drinks per day for men and 1 drink per day for women)

  • Eat a lot of red or processed meat

The colon and rectum

The colon and rectum are part of your digestive system. Food goes from your stomach, through your small intestine, then into your colon. As it travels through the colon, water is removed and the waste that is left (stool) becomes more solid. The muscles of your intestines push the stool toward the sigmoid colon. This is the last part of the colon. The stool then moves into the rectum. It's stored there until it’s ready to leave your body during a bowel movement.

How colorectal cancer starts

Polyps are growths that form on the inner lining of the colon and rectum. Most are benign, which means they aren’t cancer. But over time, some polyps can become cancer. These are called malignant. This happens when cells in these polyps start to grow out of control. In time, the cancer cells can spread to more of the colon and rectum. The cancer can also spread to nearby organs or lymph nodes, and even to other parts of the body, like the liver or lungs. Finding and removing polyps before they become cancer can help keep cancer from starting.

Colorectal cancer screening

Screening means looking for a health problem before you have symptoms. Screening for colorectal cancer starts with:

  • Your health history. Your healthcare provider will ask about your health history and possible cancer risk factors. Tell your healthcare provider if you have a family member who has had colorectal cancer or polyps. Also mention any health problems you have had in the past.

  • Physical exam, including a digital rectal exam (DRE). A DRE might be done as part of your physical exam. To do it, your healthcare provider puts a lubricated gloved finger into your rectum. He or she checks for any lumps or changes that could be cancer. This doesn't hurt and takes less than a minute. DRE alone is not enough to screen for colorectal cancer. You'll also need one of the tests listed below.

Screening test choices

Screening advice varies among expert groups. Many suggest that people at average risk for colorectal cancer start routine screening at age 50. But the American Cancer Society (ACS) recommends starting screening at age 45. Your healthcare provider can help you decide what's best for you. It's also important to check with your health insurance provider.

Below are the most commonly used colorectal cancer screening tests. How often you should be screened depends on your risk and the test that you and your healthcare provider choose. If you have a family history of colon cancer or are at high risk for other reasons, you may need to have screening earlier or more often.

Stool testing

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

These tests check for blood in stool that you can’t see (hidden or occult blood). Hidden blood may be a sign of colon polyps or cancer. A small sample of stool is sent to a lab where it's tested for blood. Most often, you collect this sample at home using a kit your healthcare provider gives you. Make sure you know what to do and follow the instructions carefully. For instance, you might need to not eat certain foods and not take certain medicines before collecting stool for this test.

Stool DNA test (every 3 years)

This test looks for cells in your stool that have changed DNA in them. These DNA changes might be signs of cancer or polyps. This test also looks for hidden blood in stool. For this test, you collect an entire bowel movement. This is done using a special container that's put in the toilet. The kit has instructions on how to collect, prepare, and send your stool. It goes to a lab for testing.

Visual exams

Colonoscopy (every 10 years)

This test allows your healthcare provider to find and remove polyps anywhere in your colon or rectum.

A day or 2 before the test, you'll do a bowel prep. This is a liquid diet plus a strong laxative solution or an enema. The bowel prep cleans out your colon so the lining can be seen during the test. You'll be given instructions on how to do the prep.

Just before the test, you're given a medicine to make you sleepy. Then the healthcare provider gently puts a long, flexible, lighted tube (called a colonoscope) into your rectum. The scope is guided through your entire colon. The provider looks at images of the inside of your colon on a video screen. Any polyps seen are removed and sent to a lab for testing. If a polyp can’t be removed, a small piece of it is taken out for testing. If the tests show it might be cancer, the polyp might be removed later during surgery.

You'll need to bring someone with you to drive you home after this test.

Colonoscopy is the only screening test that lets your healthcare provider see your entire colon and rectum. This test also lets your healthcare provider remove any pieces of tissue that need to be checked for cancer.

If something suspicious is found using any other colorectal cancer screening tests, you will likely need a colonoscopy.

Sigmoidoscopy (every 5 years)

This test is a lot like a colonoscopy. But it focuses only on the sigmoid colon and rectum. (The sigmoid colon is the last 2 feet or so that connects to your rectum. The entire colon is about 5 feet long.) As with colonoscopy, bowel prep must be done before this test.

You are awake during the test. But you might be given medicine to help you relax. During the test, the healthcare provider guides a thin, flexible, lighted tube called a sigmoidoscope through your rectum and lower colon. The images are displayed on a video screen. Polyps can be removed and sent to a lab for testing.

Virtual colonoscopy (every 5 years)

This test is also called a CT colonography. It uses a series of X-rays to make a 3-D image of your colon and rectum.

The day before the test, you'll need to do a bowel prep to clean out your colon. Your healthcare provider will give you instructions on how to do this.

During the test, you'll lie on a narrow table that's part of a special X-ray machine called a CT scanner. A soft, small tube will be placed into your rectum to fill your colon and rectum with air. Then, the table will move into the ring-shaped machine and pictures will be taken. A computer will combine these photos to create a 3-D image. Because the test uses X-rays, it exposes you to a small amount of radiation. This test can be done without sedation. If polyps or any suspicious changes are seen, you'll need a colonoscopy so that tissue can be removed for testing.

Talking with your healthcare provider

Talk with your healthcare provider about which screening tests might be best for you. Each one has pros and cons. But no matter which test you choose, the most important thing is that you get screened. Keep in mind that if cancer is found at an early stage during screening, it's easier to treat and treatment is more likely to work well. Cancer can even be prevented with routine screening tests.

Note: If you choose a screening test other than a colonoscopy and have an abnormal test result, you'll need to follow-up with colonoscopy. This would not be considered a screening colonoscopy, so deductibles and co-pays may apply. Check with your health insurance provider so you know what to expect.

Know your risk: You may need to be screened using a different schedule if you have a personal or family history of colorectal cancer. A different schedule might also be needed if you have polyps or certain inherited conditions. These include familial adenomatous polyposis (FAP), Lynch syndrome (hereditary nonpolyposis colon cancer, HNPCC), or inflammatory bowel disease such as Crohn's or ulcerative colitis. Talk with your provider about your health history to decide on the colorectal cancer screening plan that's best for you.

Online Medical Reviewer: Kimberly Stump-Sutliff RN MSN AOCNS
Online Medical Reviewer: Louise Cunningham RN BSN
Online Medical Reviewer: Richard LoCicero MD
Date Last Reviewed: 8/1/2020
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