Types of Colorectal Cancer Screening Tests

There are several tests available to screen for colorectal cancer. Your primary care provider can help you to understand which test is best for you, based on your personal risk and other factors. Below are the screening tests for colorectal cancer.

Colonoscopy

During a colonoscopy, your doctor checks your entire large intestine for cancer and polyps using a thin, flexible tube that has a tiny light and camera inside of it. Colonoscopy is a very common and effective test that prevents cancer by painlessly removing any polyps before they can turn into colon cancer.

Why would a doctor recommend a colonoscopy?

  • Almost all colorectal cancers begin as polyps, which are small growths on the lining of the colon or rectum. During a colonoscopy, polyps can be found and painlessly removed to prevent them from turning into cancer. If cancer is present, it can potentially be found at an earlier stage, which can significantly prolong survival.
  • Colonoscopy can be used to diagnose inflammatory bowel diseases like Crohn's disease and ulcerative colitis.
  • Colonoscopy can also be used to investigate symptoms such as frequent diarrhea, rectal or intestinal bleeding, a change in bowel habits, abdominal pain, significant weight loss, or other problems.

What does a colonoscopy involve?

  • The evening before and morning of your colonoscopy you will need to drink a bowel preparation solution to empty and cleanse your colon. A clean colon lining can be more easily and carefully examined for polyps or other suspicious findings.
  • During the procedure you will be given medication to make you relaxed and comfortable (some patients even fall asleep). Because air is used to open the colon so it can be seen, and the scope travels around bends in the colon, you may feel some cramping during the procedure.
  • Your doctor will slowly guide the colonoscope through the entire length of the large intestine while viewing it on a monitor. If polyps are found they can be painlessly removed with the colonoscope. The doctor may also take a biopsy (tissue sample), or possibly use other procedures if needed.

How long is the recovery after a colonoscopy?

  • Most patients are sedated during a colonoscopy to keep them comfortable. You will spend a short time in the recovery room while the effects of the medication wear off. Typically patients are at the hospital for about three hours. Because you might still feel groggy, you will need to arrange for someone to drive you home. Plan on resting for the remainder of the day, and eat lightly at first. Minor symptoms such as gas or bloating may be present but should disappear within a short time.

Flexible sigmoidoscopy

Flexible sigmoidoscopy is similar in procedure to a colonoscopy, except that it looks only at the lower portion of the large intestine and the rectum, instead of the entire large intestine. The test only takes a few minutes, but similar to a colonoscopy, you usually will need to do some bowel preparation beforehand to clean out your large intestine.

Fecal occult blood test (FOBT): Fecal immunochemical test (FIT) or Hemoccult II Sensa

A fecal occult blood test, or FOBT, is a simple test that checks for the presence of hidden blood in the stool. Your doctor may recommend that you have a FOBT (FIT or Hemoccult II Sensa) every year if you are at least 50 years old and at average risk. Recent studies have suggested the screening for colorectal cancer begin at 45 instead of at age 50. An FOBT can be done in the privacy of your home and involves obtaining a small stool sample, which is checked for hidden blood. These tests are simple, inexpensive and quick, but is important to follow instructions carefully.

  • The guaiac based tests (Hemoccult) detect any blood found in the stool, including animal blood. For instance, eating a rare steak the day before the test may change the test results. Certain medications can also interfere with results and are therefore included in the instructions.
  • The FIT only detects human blood which makes it a bit easier to use, but both tests are appropriate for screening in average risk people.

If your FOBT comes back positive, a colonoscopy will be needed to look for polyps or any other cause for blood in the stool.

Stool DNA Test (Cologuard)

The multi-target stool DNA test (Cologuard) checks for DNA and blood in your stool which could be an indicator of colorectal cancer or polyps. For average risk patients, it is done every three years as long as the test is negative.

Your provider orders the test kit which is delivered to your home. Instructions are included in the box, as well as a container to collect the sample. The test requires one bowel movement and the sample container is mailed back to the manufacturer of Cologuard in the same box. After the test is completed, the results will be sent to your provider.

If your Cologuard test comes back positive, a colonoscopy will be needed to look for polyps or any other cause for blood in the stool.

CTC (Virtual Colonoscopy)

For average risk patients, CTC is done every five years as long as the test is negative. Virtual colonoscopy is a special type of computerized tomographic (CT) examination of the colon that looks for polyps or other findings. The test takes only a few minutes and does not require the use of anesthesia.

If your CTC test is positive, a colonoscopy will be needed to remove polyps or any other findings.