Studies Show Effectiveness of Colon Screenings with Easier Preparation
Article date: June 21, 2012
By Stacy Simon
Two recent studies found colon screenings that require a less intensive preparation than a colonoscopy are useful in finding pre-cancerous polyps, or growths. The usual preparation – eating a special diet, drinking up to a gallon of a liquid laxative, and sometimes enemas to clean the colon – is unpleasant for many people and may discourage them from getting recommended screenings.
Regular colon screening is important because it can prevent cancer or find it early when it is easier to treat. This is because some polyps can be found and removed before they have the chance to turn into cancer. The American Cancer Society recommends colon cancer screening (there are several acceptable methods) for everyone starting at age 50, though some people may need to start at a younger age.
Researchers from the University of Pittsburgh and colleagues found that a flexible sigmoidoscopy significantly reduced colorectal cancer death rates and the rates of new cases. Sigmoidoscopy is one of the colon screenings recommended by the American Cancer Society. During this test, the doctor looks at part of the colon and rectum with a sigmoidoscope – a flexible, lighted tube with a small video camera on the end. The doctor can find polyps and remove them with a small instrument passed through the scope. A sigmoidoscope is a shorter version of a colonoscope, which a doctor uses to view the entire colon during a colonoscopy.
Preparation for a sigmoidoscopy may also involve a special diet, laxatives, or enemas to clean the colon. However, it is generally easier to tolerate than the preparation for a colonoscopy. Most people do not need to be sedated for a sigmoidoscopy, and therefore, may drive themselves home from the procedure.
In the study, about 155,000 people were assigned randomly to either sigmoidoscopy screening or “usual care” and then followed for about 12 years. Those in the screening group were screened when they joined the study, then either 3 or 5 years later. People in the usual care group only received screening if they asked for it, or if their doctor recommended it. Researchers found that the screening group had a 21% lower rate of new colorectal cancer cases and a 26% lower rate of colorectal cancer deaths than the usual care group.
The study did not directly compare sigmoidoscopy with colonoscopy. However, the researchers concluded that screening with sigmoidoscopy significantly reduced both new cases and deaths due to colorectal cancer. In addition, the easier colon preparation may encourage more people to get screened.
The study was published early online May 21, 2012 in the New England Journal of Medicine.
Laxative-free computed tomographic colonography
In another study, funded by the American Cancer Society, researchers from Massachusetts General Hospital and University of California, San Francisco tested a kind of screening called computed tomographic colonography (CTC), also called “virtual colonoscopy” that doesn’t require a laxative preparation. While the standard virtual colonoscopy is included in the American Cancer Society colon screening guidelines, laxative-free CTC is not yet available to patients outside of studies.
Lead researcher, Michael E. Zalis, MD, said, “While we know that colon screening can save lives, not enough people participate, in part because of the discomfort of the required laxative preparation. In our study, the laxative-free form of CT colonography performed well enough that it might someday become an option for screening, which we hope would increase patient participation.”
Preparation for the screening done in the study required 2 days of a low-fiber diet and drinking small amounts of a dye to color the fecal matter in the colon. During the screening, a computer recognizes the dyed material and deletes it from the image that is used to check for polyps. Sedation is not needed. The patients in the study then had regular colonoscopy performed sometime in the next 5 weeks. This allowed the researchers to compare the results of the CT colonography with colonoscopy.
In the study, published in the May 15 issue of Annals of Internal Medicine, 604 patients completed the screening. Results showed that laxative-free CTC found 91% of polyps 10 mm or larger, which is as effective as a regular colonoscopy. While it was less effective at detecting smaller polyps, the smaller polyps are less likely to develop into cancer. More patients preferred CTC to colonoscopy. This kind of screening would require an additional procedure if any polyps were detected that needed to be removed.
Zalis said, “If we can validate that this form of CT colonography performs reasonably well for screening and is easier for patients, it could have a significant impact on reducing the incidence of colon cancer and related cancer deaths.”
Reviewed by: Members of the ACS Medical Content Staff
Citations: Colorectal-Cancer Incidence and Mortality with Screening Flexible Sigmoidoscopy. Published online May 21, 2012 in the New England Journal of Medicine. First author: Robert E. Schoen, MD, MPH, University of Pittsburgh.
Diagnostic Accuracy of Laxative-Free computed Tomographic Colonography for Detection of Adenomatous Polyps in Asymptomatic Adults. Published in the May 15, 2012 issue of Annals of Internal Medicine (Vol. 156, No. 10). First author: Michael E. Zalis, MD, Massachusetts General Hospital, Boston.
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