Screening Options for Colon Cancer Prevention By Diana Rodriguez | Medically reviewed by Christine Wilmsen Craig, MD and Farrokh Sohrabi, MD Different tests can spot colon cancer. Heres how to prepare for them. Early-stage colon cancer has very subtle symptoms, if any. It generally begins as a polyp, a growth that protrudes from the colon wall. Some polyps can turn into cancer. With regular screening tests, these polyps may be detected and removed before they become cancerous. Thats why regular screening for people over age 50 and those at high risk of developing colon cancer is so important. Colon Cancer Screening: Tests to Know There are a number tests that screen for colon cancer. These include: Fecal occult blood test (FOBT). A series of stool samples are taken and examined for hidden blood to screen for colorectal cancer. Some polyps and cancers bleed. Finding blood on the test doesn’t necessarily mean that you have cancer (the blood could come from a hemorrhoid, for example), just as the absence of blood doesn’t mean that you don’t have cancer (not all cancers bleed, and some only bleed intermittently). If blood is found in the stool sample, your doctor may order a colonoscopy for further evaluation. The American Cancer Society recommends the home FOBT test in which samples are taken for a few days in a row, rather than the one-sample test done in a doctor’s office. No real preparation is needed, but your doctor may ask you to follow a certain diet for a few days before the test. In August 2014, the U.S. Food and Drug Administration approved a new at-home fecal screening test to help detect colon cancer. The test requires a stool sample to be ordered by your doctor, says Janice Rafferty, MD, a clinical professor of surgery, the Carl and Edyth Lindner endowed chair, and the chief of the division of colon and rectal surgery at the University of Cincinnati in Ohio. The test detects abnormal DNA and blood in the stool and is appropriate if you’re over age 50 and have no increased risk factors for colorectal cancer or a personal history of colorectal cancer. “This test is highly accurate in detecting the DNA found in an advanced polyp or a cancer,” Dr. Rafferty says. “If the test is positive, it must be followed up with a colonoscopy.” Double contrast barium enema (DCBE). In this procedure, liquid containing a contrast dye (to help it show up on an X-ray) is introduced into the colon through the rectum. Air is pumped into the colon so it can be more clearly seen, then the area is X-rayed to check for polyps or abnormal lesions. The entire colon can be examined, but some small polyps and cancers may not be seen on this test. If a polyp is found on the X-ray, a colonoscopy will be done as a follow-up test. Your colon will need to be fully cleaned out before the test, but you will not need a sedative. Virtual colonoscopy (also called CT colonography). This is a computed tomography (CT) scan of the colon to check for the polyps or abnormal lesions that may indicate colorectal cancer. During the procedure, you lie on a table while a machine moves around you and takes pictures of your abdomen. Once again, this test allows the entire colon to be examined, but some small polyps and cancers may not be seen. This test is often performed on people who may not be comfortable taking more invasive colorectal cancer screening tests. “CT colonography is a newer and less invasive way to screen for colorectal cancer,” Rafferty says. “It’s a special CAT scan of the colon, with special software that allows the radiologist to reconstruct images of the lining of the colon.” For this test, a small tube is inserted into the rectum to inflate the colon with air for better images to be seen, But no sedation is required. Medicine is necessary to clean out the colon in preparation for the virtual colonoscopy procedure. If polyps are found, a standard colonoscopy will need to be performed to evaluate or remove them. Flexible sigmoidoscopy. This test is similar to a colonoscopy, but the tube is shorter and is therefore able to view only the lower portion of the colon. If polyps are found, a colonoscopy may be performed to check for polyps in the rest of the colon. A flexible sigmoidoscopy is less invasive than a colonoscopy, but it’s still a sensitive screening test. It requires a less-thorough colon cleaning before the test. Colonoscopy. In this procedure, a narrow, flexible tube is inserted through the rectum into the colon. The tube contains a light and a tiny video camera, which allows the doctor to see and evaluate the entire colon on a monitor and check for polyps. If a polyp is found, it will be removed and examined for cancer cells. “Colonoscopy is currently the most sensitive and specific screening test for colon cancer because it allows the doctor to visualize the lining of the large intestine,” Rafferty says. Colonoscopy offers the most comprehensive view of the colon and is therefore more likely than other tests to detect polyps and abnormal lesions. While it’s also the most invasive and requires the most preparation, if it reveals polyps, they can be removed right away. If a polyp is found during most of the other tests, a colonoscopy will then be needed anyway, as a second procedure, to get rid of it. The day before the test, your doctor will have you drink a prescribed liquid solution to clean out your colon. The test is often done in a hospital setting and under sedation — chances are you won’t remember any of it — and you’ll need someone to drive you home after the procedure. Your doctor will give you a list of instructions to follow in the days before and after the test. While most people get squeamish just reading about these tests, they can detect colon cancer early, sometimes even before it’s had a chance to form. If done regularly, screening for colon cancer can save your life. Last Updated: 9/23/2014
Posted on: Thu, 30 Oct 2014 11:10:36 +0000