In 2008 the American Cancer Society, the U.S. Multi-Society Task Force on Colorectal Cancer, and the American College of Radiology published a joint guideline on colorectal cancer screening and surveillance intended to provide a “practical guideline for physicians to assist with informed decision making related to colorectal cancer screening.”12
The United States Preventive Services Task Force also updated their colorectal cancer screening recommendations which were previously issued in 2002.4
These guidelines were followed by the release of the American College of Gastroenterology Guidelines for colorectal cancer screening published in early 2009. Although largely similar, there are differences among these three sets of guidelines that should be considered when counseling patients about colorectal cancer screening. The following sections briefly summarize these recommendations and highlight important differences.
Joint Guidelines of the American Cancer Society, the US Multi-Society Task Force, and the American College of Radiology
The review process for updating these guidelines included dividing colorectal cancer screening tests into two phases. The first phase examined the evidence behind using stool tests which included guiac-based FOBT (gFOBT), fecal immunohistochemical tests (FIT), and stool DNA tests (sDNA). The second phase focused on structural exams which included flexible sigmoidoscopy, colonoscopy, double-contrast barium enema (DCBE), and CT colonography (CTC).12
The guidelines recommend colorectal cancer screening for all average-risk women and men aged 50 years and older. While the guidelines note that all of the above mentioned tests are acceptable choices, individuals should have the opportunity to make an informed decision regarding their choice of test. However, the guideline development committee felt that colon cancer prevention should be the goal of screening. Therefore, tests that are designed to detect early cancers as well as adenomatous polyps are encouraged over those tests that primarily detect cancer. Thus, structural exams, such as flexible sigmoidoscopy, colonoscopy, DCBE, and CTC, are preferred over stool based exams (gFOBT, FIT, sDNA).
As noted above, the guideline development committee encourages tests designed to detect both early cancer and adenomatous polyps. There are, however, multiple options in this category (sigmoidoscopy, colonoscopy, DCBE, and CTC) and the guidelines do not specify a preferred structural test. A key issue when discussing screening options with patients is that for all tests other than colonoscopy, colonoscopy is the recommended test to follow-up on any significant findings found using other screening methods. Another key issue is the recommended screening interval for each screening option.
Based on the 2008 joint guidelines, the recommended testing interval for flexible sigmoidoscopy is every 5 years. Additional important issues to consider with flexible sigmoidoscopy include: the need for a partial or full bowel preparation prior to the procedure, sedation is generally not used so discomfort during the procedure may be present, and that the protective effect of sigmoidoscopy is limited to the reach of the sigmoidoscope, the distal colon.
The recommended screening interval for colonoscopy is every 10 years. Key issues when considering colonoscopy are the need for a complete bowel preparation prior to the procedure and the use of sedation during the procedure. Conscious sedation is used during most colonoscopies so patients usually require a chaperone for transportation and will generally miss a day of work. Another important consideration is the risk of complications such as perforation and bleeding, most of which is associated with polypectomy.
The recommended time interval for CT colonography (CTC) is every 5 years. Similar to colonoscopy, a complete bowel preparation is required. Risks associated with CTC are low but colon perforation has been reported. Additional important issues to consider with CTC is the need for optical colonoscopy for patients who have polyps of >= 6 mm on CTC and the question of how to approach extracolonic abnormalities identified by CTC.
As noted above, while “structural” exams are preferred in the “joint guidelines”, tests that primarily detect cancer, gFOBT, FIT, and sDNA, are still viable screening options. Both gFOBT and FIT should be done on an annual basis. Given variability in the availability of stool tests, the guidelines highlight the importance of using high sensitivity tests as well as the importance of programmatic, serial, annual testing with gFOBT or FIT if tests are negative. Key issues regarding sDNA include the cost of each test which is significantly higher than gFOBT or FIT tests and that the interval for sDNA testing following negative testing is uncertain. Again, any positive stool tests should be followed by a colonoscopic evaluation.