Colon Cancer Screenings
There are several tests that may be recommended to test for colon cancer.
Age & Risk Factors:
For people who have normal risk for colon cancer, it is recommended to get screened at regular intervals beginning at age 50. Those who have a higher risk factor for developing colon cancer may be advised by their doctor to get screenings before the age of 50 or more frequently. These risk factors include but are not limited to:
- family history of colorectal cancer
- family history of polyps
- sufferers of inflammatory bowel disease (ulcerative colitis; Crohn’s diease)
The type of colon cancer screening test that is administered is based on a number of factors, including but not limited to:
- heredity risk factors
- previous medical history
- potential harms or risks of the test
- preparation required prior to the test (dietary restrictions; cleansing of the colon)
- convenience of test (whether it can be performed at home or at the doctor’s office)
- cost of the test and insurance benefits available for the test
Polyps and colorectal cancers can bleed, and this test will find tiny amounts of blood in the feces if present. The detection rate on these tests is fairly high – studies show that, when performed every 1 to 2 years ages 50 to 80, the gFOBT test can help reduce the number of colorectal cancer deaths by as much as 33%. If FOBT is the only type of colorectal screening method, the U.S. Preventative Services Task Force recommends that these tests be repeated yearly.
There are currently two types of FOBT that are approved by the Food and Drug Administration (FDA) for colorectal screening:
Guaiac FOBT, which uses a chemical to detect trace amounts of the blood protein known as hemoglobin in the feces. However, there are dietary restrictions that need to be followed prior to this test, as it can detect hemoglobin in some foods like red meat.
Fecal immunochemical test (FIT, or iFOBT), which uses antibodies to detect only human hemoglobin, thereby no dietary restrictions are required prior to the test. For each of these tests, the patient will be provided with a sample kit and instructions, and then will return the sample to their doctor.
Unlike a traditional colonoscopy, a virtual colonoscopy uses CT scanning to produce images of the colon without insertion of a colonoscope or sedation. The only difference between a regular CT and a virtual colonoscopy is that air or carbon dioxide will be pumped into the colon to expand it, and patients will still need to thoroughly cleanse the colon. The accuracy of virtual colonoscopy is similar to standard colonoscopy, but is less invasive and does not carry the risks of standard colonoscopy.
This test is also done outside the body, and is performed after the patient has been given an enema with a barium solution, which will outline the colon, rectum, and any irregularities on the images. This test has not been shown to be as diagnostically sensitive as colonoscopy, and is only recommended if there is a reason a patient cannot undergo a standard colonoscopy.
Likely the most common procedure, this is one of the most diagnostically sensitive tests, gives the doctor the ability to view the entirety of the rectum and colon, and it is possible to perform a biopsy or polypectomy during the colonoscopy if found necessary. While the standard colonoscopy is the most sensitive, it is not fully conclusive and small polyps, nonpolypoid lesions, and some cancers may not be detected. A thorough cleansing of the colon will be required, and sedation is almost always used, which will require that the patient be driven home afterward.