Colorectal Cancer Screening

Colorectal cancer is a type of cancer that starts in the colon or rectum. It is the fourth most common cancer diagnosed in the United States and is increasing in incidence and prevalence. Around 10% of colorectal cancer cases in the U.S. are diagnosed in individuals under 50 years of age.

Colorectal cancer develops from polyps. Polyps are growths in the colon that over many years undergo cellular changes that can develop into a cancer. The goal of colorectal cancer screening is to identify high risk polyps and remove them before a cancer develops. The most effective method to identify polyps and remove them to prevent colorectal cancer is with colonoscopy.

According to the American Cancer Society, most people with an average risk for colorectal cancer should start regular colorectal screenings at age 45. Your doctor may recommend starting regular screenings younger or at more frequent intervals if you have:

• A personal or strong family history of colorectal cancer or certain types of advanced polyps.
• A personal history of inflammatory bowel disease (Crohn’s disease, ulcerative colitis or primary sclerosing cholangitis).
• A family history of hereditary colorectal cancer syndrome (Lynch syndrome, Peutz-Jeghers syndrome, Familial adenomatous polyposis syndrome, etc.).

Your provider will work with you to determine which screening option is best for you based on your age, family history, risks and other factors. One or more of these tests may be recommended:

Colonoscopy

This is the most common procedure for screening and diagnosing colon cancer. This test does require a bowel preparation to clean the bowel out the night before. During the procedure, your provider uses a thin, flexible tube with a light and tiny camera at the end to examine the rectum and entire length of the colon. Any polyps or abnormal tissue can be fully removed for testing.

The procedure itself is not considered painful. It is typically performed with either conscious sedation with medication for anxiety and pain or monitored anesthesia care (MAC) with an anesthesiologist administering medication to keep you comfortable. It is also possible to do this test with no sedation, if you prefer. Discuss these options with your provider to choose what is best for you.

Stool Tests

Stool tests are an alternative to colonoscopy. The two most common options are stool DNA tests and fecal immunohistochemical tests (FIT). These are at-home tests that require collection of a stool sample that are sent to the lab for testing. The stool DNA test looks for blood in the stool as well as DNA in the stool to indicate if an advanced polyp is present in the colon. The FIT test evaluates blood in the stool. If either test is positive, the next step is to undergo a colonoscopy.

Other Screening Tests

Other modalities that are available but not commonly used include the following:

Blood Tests

The recently FDA-approved blood test is used to detect abnormal DNA in the bloodstream. This test does not detect pre-cancerous lesions like polyps, it is only used to identify if cancer is already present. The blood test is 83% effective in detecting colon cancer. This is not considered a cancer prevention test. Patients who test positive will still need to undergo a colonoscopy to confirm cancer.

Flexible Sigmoidoscopy

This procedure is performed with a thin, flexible tube with a light, camera and other tools to examine the inside of the rectum and part of the long intestine for polyps or growths. A bowel preparation with two enemas is required the day of the procedure. This procedure can be done with or without sedation. When abnormal results are found on flexible sigmoidoscopy, follow-up with colonoscopy is needed for further evaluation.

CT Colonography

A non-invasive procedure that uses a CT-scan to create highly detailed 3D images of the colon and rectum. A bowel preparation is required prior to the CT-scan. The images are examined by a provider to look for polyps or growths in the colon and rectum. When abnormal results are found on CT colonography, follow-up with colonoscopy is needed for further evaluation.

Your colon must be as empty as possible for the gastroenterologists to get a clear view of the colon and rectum during the procedure. The endoscopy team will provide you with detailed instructions beforehand. You may be asked to:

• Follow a special diet called a low residue diet three to five days prior to the procedure. This is to avoid foods that move through your bowel slower and may limit the ability to clear the bowel for the colonoscopy.
• Take over-the-counter or prescription laxatives to clear the bowel.
• Adjust other medications.
• Fasting from food or water before the procedure.

During colonoscopy, the provider advances the colonoscope, or scope, from the rectum into the colon.  A small camera mounted on the scope transmits a video image from inside the large intestine to a computer screen, allowing the provider to carefully examine the intestinal lining and look for:

• Bleeding
• Irritated, red or swollen tissue
• Polyps (non-cancerous growths that can become cancerous)

The provider may remove polyps or take samples from abnormal-looking tissues for testing. The procedure, called a biopsy, allows the doctor to later look at the tissue with a microscope for signs of disease. Polyps are fully removed to prevent the risk of colon cancer in the future. Polyps are common in adults and are usually harmless. However, most colorectal cancer begins as a polyp, so removing polyps early is an effective way to prevent cancer.