Expert Health Articles

Colon Cancer Screening Methods

Brianne Hottinger, RN, Oncology Nurse Navigator

The Armes Family Cancer Care Center

Colon cancer is the third most common cancer in men and women in the United States. According to the American Cancer Society, it is estimated there will be over 101,420 new cases of colon cancer and 44,180 new cases of rectal cancer in 2019. The overall lifetime risk for development of colon cancer is about 1 in 22 for men and 1 in 24 for women.

The good news, however, is that the death rate from colorectal cancer has been dropping in recent years largely in part by proper screening. The American Cancer Society recommends screening begins at age 45 and ends at the age of 75 unless encouraged by a physician to extend screening.

There are multiple ways to screen for colorectal cancer. The most efficient screening practice is the colonoscopy. If you choose any other form of screening test and the result is abnormal, it should be followed up with a colonoscopy. Screening measures can be divided into two groups: stool-based tests and visual exams.

Stool-based tests check the stool for signs of cancer. They are less invasive and need to be completed more often than the colonoscopy. The first type of stool-based test is the fecal immunochemical test (FIT). This test can be done in the privacy of your own home and requires a small amount of stool to be collected. There are no dietary restrictions before the test, and collecting the sample can be done quickly and easily. If the FIT kit is positive, meaning that blood is detected in the stool, the patient will be referred for a colonoscopy to look visually for cancer in the colon and rectum.

Another stool-based test is the guaiac-based fecal occult blood test (gFOBT). This test is similar to the FIT in that it looks for blood in the stool. This test can also be completed at home with collected stool, and it allows you to collect more than one sample. As with the FIT kit, if the results are positive, the patient will require a colonoscopy. The gFOBT does have drug and food restrictions that the FIT does not.

Finally, there is a stool DNA test. This test looks for abnormal DNA from cancer or polyp cells. Colorectal cancer often has DNA mutations, and this test will look for those cell changes in the stool. This type of test should be done every three years but will also require a colonoscopy if DNA changes are found in the sample.

The second group of screenings are visual exams, which include CT colography, flexible sigmoidoscopy and colonoscopy. A CT colography takes pictures of the colon and rectum to look for polyps and cancer. Although less invasive, if a polyp or cancer is seen, a colonoscopy will follow to remove it or further screen.

The flexible sigmoidoscopy looks at the entire rectum, but less than half of the colon. This test is not used often due to the reduced amount of colon visualized. Some polyps and cancer may be further along in the colon and will not be detected with this type of visual screening.

Finally, the gold standard of colorectal screening is the colonoscopy. A physician uses a colonoscope to visualize the entire length of the colon and rectum. There is a bowel prep and likely a diet that will need to be followed in the days leading up to the exam. During the colonoscopy, polyps can be removed, and samples can be sent to pathology for diagnosis. If the colonoscopy is clear and there are no abnormal findings, the test will not need to be repeated for 10 years.  

For further information on colorectal cancer screenings, speak with your primary care physician about guidelines and the type of screening that is best for you.