Early diagnosis of colon cancer is the key to surviving the disease. When detected in its early stages through screening tests, 90% of colon cancer cases are preventable, treatable, and beatable.
The Centers for Disease Control (CDC) recommends the following tests for colorectal cancer screening: colonoscopy, sigmoidoscopy, and at-home stool testing.
Stool-Based Tests
Stool-based tests are non-invasive colorectal cancer screening options. No special bowel preparation (no laxatives or enemas) is required for a stool-based test. However, if the test does show abnormal signs of blood or a possible cancer or pre-cancer, a colonoscopy will be needed to confirm the result, and possibly to remove any abnormal findings or polyps. It’s important to remember the cause of an abnormal result may be a non-cancerous condition, such as ulcers or hemorrhoids.
Stool-based tests are not the best option for everyone. They are recommended for people who have an average risk for colorectal cancer: no personal history of pre-cancerous polyps, no colorectal cancer that runs in the family, or no other risk factors.
- Fecal immunochemical test (FIT) and guaiac-based fecal occult blood test (gFOBT) are non-invasive tests used to find tiny amounts of blood in the stool that could be a sign of cancer or large polyps. Patients take these tests at home with a kit they receive from their doctor’s office, along with instructions on how to do the test and return it so it can be checked. Each test detects blood differently, but neither test can tell where the blood might be coming from. That’s why any abnormal result will need to be followed up with a colonoscopy. Stool tests like these need to be done every year.
- Stool DNA testing (Cologuard®) is another type of non-invasive test to check for colorectal cancer. It looks for certain DNA or gene changes that often get into the stool and are sometimes found in pre-cancerous growths and cancer cells. It also checks for blood in the stool, which can be a sign of cancer. If a stool DNA test finds something abnormal, a colonoscopy will be needed to follow-up on the findings. This kit arrives in the mail to your home and is done every 3 years.
Visual Tests
Visual or structural tests are invasive tests that look inside the colon and rectum for abnormal areas that might be cancer or polyps. If a stool-based test was done first and had an abnormal result, a visual test can help find out why.
- Colonoscopy uses a flexible lighted tube with a small camera on the end to look at the entire length of the colon and rectum. If polyps are found, they may be removed during the test. To prepare for the test, you may be asked to follow a special diet for a day or two before the test. You will also need to clean out your colon with strong laxatives (called a bowel prep) and sometimes with enemas, as well. Most people are sedated during the test. If nothing is found during the test, you won’t need another one for 10 years.
- CT colonography (also called virtual colonoscopy) is a scan of the colon and rectum that produces detailed cross-sectional images so the doctor can look for polyps or cancer. It requires bowel prep, but no sedation. Air is pumped into the rectum and colon, and then a CT scanner is used to take images of the colon. If something is seen that may need to be biopsied, a follow-up colonoscopy will be needed. CT colonography must be done every 5 years.
- Flexible sigmoidoscopy is not widely used for colorectal cancer screening in the U.S. It’s like a colonoscopy, but only looks at a certain part of the colon and rectum instead of looking at the entire length of the colon and rectum. If polyps are found, they may be removed during the test, or you may need to have a colonoscopy later. Bowel prep may be required, but is not as extensive as the one used for colonoscopy. Most people do not need to be sedated during this test. If polyps or suspicious areas are seen, a colonoscopy will be needed to look at the rest of the colon. Flexible sigmoidoscopy must be done every 5 years.
Regular screening is one of the most powerful ways to prevent colorectal cancer. If polyps are found during colorectal cancer testing, they can usually be removed before they have the chance to turn into cancer. Testing can also result in finding cancer early, when it’s smaller and might be easier to treat.
There is no single “best test” for any person. Each test has advantages and disadvantages. Talk to your doctor about the pros and cons of each test, and how often to be tested. Which test to use depends on—
- Your preferences.
- Your medical condition.
- The likelihood that you will get the test.
- The resources available for testing and follow-up.