The combination of sigmoidoscopy and fecal immunochemical test (FIT) detects advanced proximal (right-sided) tumors better than either test alone, according to a new study in Clinical Gastroenterology and Hepatology, the official journal of the American Gastroenterological Association (AGA) Institute. African Americans, the elderly and women have a higher incidence of proximal colon tumors.
"Our study results suggest that colorectal cancer (CRC) screening with sigmoidoscopy and FIT is superior to and more effective than screening with either alone, making this combination a viable and useful screening option," said Jun Kato, MD, of Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, and lead author of the study. "This strategy should be considered, especially in communities that are not capable of colonoscopy screening."
Although CRC is one of the leading causes of cancer deaths in many countries, CRC patients often have no associated symptoms. Therefore, a large number of organizations and expert panels have recommended screening for asymptomatic adults beginning at age 50.
There have been no studies to evaluate the sensitivity of a one-time screen that utilizes both flexible sigmoidoscopy and FIT to detect advanced colorectal tumor formation. This combination was recommended as one strategy for CRC screening by the U.S. Preventive Services Task Force in 2008. While no screening test is perfect, each test has unique advantages, has been shown to be cost-effective, and has associated limitations and risks.
In a study conducted in Japan, doctors analyzed data from 21,794 asymptomatic persons who had undergone colonoscopy and FIT. When colonoscopy was performed for a positive FIT result alone, for a positive sigmoidoscopy finding and for either a positive FIT result or sigmoidoscopy finding, the sensitivities in detection of advanced proximal neoplasia were 22.3 percent, 16.3 percent and 31.7 percent, respectively. The sensitivities for detection of proximal invasive cancer were 58.3 percent, 8.3 percent and 62.5 percent, respectively.
The incremental yield of advanced neoplasm detection by using both tests is approximately 10 percent. FIT adds the most in terms of finding proximal cancers in a screening program that uses both tests. In addition, FIT has been replacing the standard guaiac-based test and is expected to become more prevalent. Therefore, this study is relevant to CRC screening strategy in the near future. While the optimal screening interval is still unknown, repeated testing is necessary, even for this combined strategy.
The use of sigmoidoscopy as a screening test for CRC does not allow gastroenterologists to view the right side of the colon to screen for polyps, only the rectum and the lower end of the colon. If a polyp or abnormality is found, patients may require a regular colonoscopy for further evaluation. Right-sided adenomas cannot be viewed using a sigmoidoscopy.
"Colonoscopy, which provides the most comprehensive view of the colon, is the definitive test for CRC screening. Colonoscopies allow gastroenterologists to view the entire colon and rectum for polyps or cancer and during the same exam remove pre-cancerous polyps," added John Inadomi, MD, AGAF, chair, AGA Institute Clinical Practice & Quality Management Committee. "It is the test most gastroenterologists recommend as the single best screening exam for CRC. It is the only method that combines both screening and prevention (by removal of pre-cancerous polyps)."
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