What is cancer screening? Why is it important?
Screening is looking for cancer before a person has any symptoms. With colon cancer, screening can also PREVENT cancer by finding and removing polyps which can eventually become cancer. Almost all colorectal cancers begin as precancerous polyps (abnormal growths) in the colon or rectum. Such polyps can be present in the colon for years before invasive cancer develops, and they may not cause any symptoms. Screening can help find cancer at an early stage and can help avoid the disease entirely.
Routine colorectal screening is recommended for all people aged 50 and older. Screening may be recommended to begin earlier for patients with a family history of colorectal cancer or other risk factors. Always talk to your doctor about when you should start getting screened and which screening method is right for you.
It is important to remember that your doctor does not necessarily think you have cancer if he or she suggests a screening test. Screening tests are often given when you have no cancer symptoms. Screening tests may be repeated on regular basis. If a screening test is abnormal, you may need to have more tests done to find out if you have cancer. These are called diagnostic tests.
Screening for colorectal cancer helps decrease the number of deaths from the disease.
How can I get screened?
A colonoscopy is a procedure where a long, lighted tube is inserted into the rectum and examines the entire colon while the patient is under sedation. Colonoscopies can find and remove pre-cancerous growths/polyps before they come cancer. The patient must completely empty the bowel with prep beforehand. There is a small risk from the procedure and medication. Colonoscopies are the most expensive screening choice.
A sigmoidoscopy is a procedure to look for polyps. Not all polyps can be removed during a sigmoidoscopy, but they can be biopsied to detect for cancer. A sigmoidscope is inserted through the rectum into the sigmoid colon. A sigmoidoscope is a thin, tube-like instrument with a light and lens for viewing. The sigmoidoscope does not view the entire colon, so some polyps or cancers could be missed. The sigmoidoscopy does not require sedation and takes only 20 minutes. A sigmoidoscopy requires enema preparation. Many primary care providers can do the test in their office and it is less expensive than a colonoscopy.
A virtual colonoscopy can detect polyps less invasively and does not involve sedation of the patient. The virtual colonoscopy is less effective in detection of flat polyps and polyps smaller than five millimeters. Prep involves a clear, liquid diet for one to three days prior. The virtual colonoscopy uses x-rays and computers to take images. Virtual colonoscopies are expensive, but less so than a colonoscopy. If polyps or other abnormalities are found, a colonoscopy will be required.
Fecal Immunochemical Test (FIT or iFOBT)
The FIT or iFOBT tests for blood and involves swabbing a movement and placing on a card. The tests may not detect blood from further up the digestive track, such as the stomach. Testing is done at home with no prep and is inexpensive. If blood is detected, a colonoscopy will be required.
Guaiac Fecal Occult Blood Test (FOBT)
The FOBT tests for blood and involves swabbing a movement and placing on a card. It requires a restricted diet and multiple days of stool collection. Testing is done at home and is inexpensive. There is a high false positive rate, and the FOBT may miss tumors that bleed in small amounts or not at all. Testing must be repeated frequently. If blood is detected, a colonoscopy will be required.
The stool DNA/Cologuard test looks for blood and abnormal DNA in the stool. The test can detect precancerous polyps as well as cancers that do not bleed. The stool DNA/Cologuard test involves collecting a stool sample at home and mailing it to the laboratory. There is no prep involved. The stool DNA/Cologuard test has high detection rates of colon cancer.
Double-Contrast Barium Enema
A double-contrast barium enema involves pumping air and barium into the rectum. The solution will then show polyps or tumors on x-rays. The enema can find cancer in the earliest stage, when it is most treatable. Polyps cannot be removed during the procedure. The double-contrast barium enema involves laxative preparation. It is accurate for finding abnormalities and lesions in the colon, and is less expensive than a colonoscopy.
Your doctor can advise you about your risk for colorectal cancer and your need for screening tests.
Screening options and programs vary. Please see below for resources on screening by location: