By Tomislav Dragovich, MD, Medical Oncology and Hematology Division Chief at Banner MD Anderson Cancer Center.
Question: I know it's important to be screened for colorectal cancer. What types of screening tests are available?
Answer: Colorectal cancer is a disease affecting the colon or rectum, which make up the large intestine. The disease usually starts as a pre-cancerous growth called a polyp which, if left untreated, can transform over time into cancer. Fortunately, numerous screening tests are available to find polyps in the colon and rectum before they turn into cancer, or to detect cancers early enough to cure the disease. Colorectal screening tests include colonoscopy, sigmoidoscopy, stool testing for blood, and colonography. The type of test and the age at which testing should begin depend on personal and family history, and may differ for each person.
When a tumor develops in the colon or rectum, it can sometimes cause bleeding. The presence of blood in stool can be detected by a fecal occult blood test. A sigmoidoscopy uses a lighted instrument to check the rectum and lower colon, and any polyps can be removed or biopsied during the test. Colonoscopy is similar to a sigmoidoscopy, but the lighted scope can reach into the entire colon to identify and address any polyps. This procedure requires a cleansed colon and sedation. Colonography, or virtual colonoscopy, is a new test which includes a specialized CT scan of the colon. It also requires colon cleansing and a follow-up colonoscopy if any polyps are found.
An individual without personal or family history of colorectal polyps or cancer should start colonoscopy screening at age 50 and continue every five to 10 years, unless screening results suggest otherwise. For individuals with family history of colorectal cancer or polyps, earlier or more frequent testing, or a combination of screening tests, may be recommended. Visiting a general practitioner annually is the best way to ensure all screenings are done in a timely and appropriate manner.