The American Cancer Society (ACS) estimates that 1 in 22 men and 1 in 24 women in the U.S. develops colorectal cancer at some time during their lives. The National Cancer Institute expects 140,600 patients to be diagnosed with and more than 51,000 to die of cancers of the colon or rectum this year.
Early detection offers the best chance of survival.
The good news is that when diagnosed early, colorectal cancer patients generally have positive outcomes. Approximately 90% of patients who are diagnosed when cancer is localized within the colon or rectum survive at least five years, and among those whose cancers are caught after spreading to nearby structures or lymph nodes, about 70% survive at least five years.
When cancer has spread to distant organs, however, the five-year survival rate drops to around 15%. Fortunately, a variety of screening tests are available to help detect colorectal cancer early, when it can be treated most successfully. The U.S. Preventive Services Task Force (USPSTF) recommends screening for those aged 50–75, and the American Cancer Society recommends that people at average risk of colorectal cancer undergo screening at age 45. The ACS updated its recommendation in 2018 in light of data showing that colorectal cancer was increasingly being diagnosed in younger adults. Talk to your doctor about your risk of colorectal cancer to determine when to begin or whether to continue screening.
You have a choice in how screening is done.
When you hear “colorectal cancer screening,” it’s likely that you imagine colonoscopy. While colonoscopy is a common and effective way to screen for cancers of the rectum and colon, other choices are available.
For those at average risk and with no history of precancerous polyps, stool-based tests provide an easy, non-invasive way to screen for colorectal cancer. Patients can simply get a kit from the doctor’s office, collect a sample at home, and follow the instructions for delivering the sample to the lab. Be aware, however, that stool-based screening tests are not as sensitive as colonoscopy and miss some polyps and cancers. Depending on the specific type of test, it should be repeated every one to three years.
Visual colorectal screening tests provide an actual look into the colon and rectum, allowing doctors to more accurately identify abnormalities such as polyps and tumors. Because they more effective than stool-based tests, they don’t have to be repeated as frequently.
Similar to a colonoscopy, this screening test uses a sigmoidoscope—a lighted camera on a long, flexible tube that’s about ½” in diameter—to examine the rectum and only the lower third of the colon. Prior to the test, the bowel must be cleansed using laxatives; however, less extensive bowel prep may be required for this test than for colonoscopy, and most people don’t require sedation. Flexible sigmoidoscopy should be repeated every five years.
A colonoscope is longer than a sigmoidoscope, allowing the doctor to examine the entire length of the colon. Sedation is typically used, so it’s necessary to arrange for a ride home after the procedure and to take the rest of the day off work and away from important responsibilities. If polyps or other abnormalities are found during a colonoscopy, they can be removed and, if appropriate, sent for biopsy. Colonoscopy should be repeated every ten years.
CT Colonography (“Virtual Colonoscopy”)
A less invasive alternative to colonoscopy and flexible sigmoidoscopy, CT colonography allows doctors to look for signs of colorectal cancer using CT imaging rather than a camera inserted into the body. Bowel preparation is required, but sedation is not. A small, flexible tube is inserted only two inches into the rectum in order to pump carbon dioxide into the bowel. This allows the radiologist to capture the clearest possible images for accurate screening. Virtual colonoscopy should be done every five years.
Virtual colonoscopy has the advantage of allowing doctors to visually examine the entire length of the colon while eliminating the need for sedation and reducing the risk of colon perforation that is associated with colonoscopy. Many patients who cannot undergo or who struggle to tolerate a traditional colonoscopy are able to complete a CT colonography.
The USPSTF has assigned CT colonography a grade of “A,” qualifying it for mandatory coverage by private insurance companies participating in the insurance exchange. Medicare does not currently cover the procedure, but a bill has been introduced in Congress to provide Medicare coverage for virtual colonoscopy. Before booking an appointment for any medical procedure, check with your insurance company to determine your coverage to avoid unexpected charges.
Virtual Colonoscopy at Iowa Radiology
Iowa Radiology provides CT colonography at its location in downtown Des Moines. The entire test takes just 15 minutes, and you can return to your regular activities immediately afterward. Click the link below to learn more about CT scans, including virtual colonoscopy.
 “Cancer Stat Facts: Colorectal Cancer.” Cancer.gov. National Cancer Institute Surveillance, Epidemiology, and End Results Program, National Institutes of Health, 15 April 2019. Accessed 29 July 2019.
 “American Cancer Society Updates Colorectal Cancer Screening Guidelines.” Cancer.org. American Cancer Society, 30 May 2018. Accessed 29 July 2019.