Colorectal cancer is the third leading cause of cancer-related deaths in the United States. However, it is also one of the most manageable. A plenary session on colorectal cancer prevention will be among the highlights of the upcoming American College of Gastroenterology Annual Scientific Meeting, October 31 to November 2 in Washington, DC.
Symposium presenters will discuss topics ranging from detection of adenomas and advanced adenomas, to the effect of diagnostic tests and the timing of those procedures on cancer detection. A group from the University of Connecticut Health Center in Farmington (Tadros M, Swede H, Anderson J, Ungemack J) will present their paper “Increased Frequency of Proximal Colon Cancer Among Non-Hispanic Blacks, Females, and Patients over Age 60 and Older.” The paper is a 2011 ACG/Olympus Award Recipient.
Moderating the symposium are Brooks D. Cash, MD, Chief of Gastroenterology at the National Naval Medical Center in Bethesda, Maryland, and Carol A. Burke, MD, director of the Center for Colon Polyp and Cancer Prevention and co-director of the Hereditary Cancer Clinic at the Cleveland Clinic in Ohio.
Dr Burke and colleagues recently published a review showing that the new fecal immunochemical tests are more sensitive than the traditional guaiac tests for detecting occult blood in stool.
Traditional guaiac tests (Hemoccult, Hemoccult II, Hemoccult Sensa) detect peroxidase activity of hemoglobin in stool. Because they cannot distinguish between peroxidase in human blood and pseudoperoxidase in foods, and because ingested vitamin C can inhibit peroxidase, patients need to follow dietary restrictions before testing. This can detract from compliance and contribute to false results if patients are not strict about the pre-test diet. Furthermore, the test gives no clue about the origin of the blood, whether stomach, colon, or small bowel. Test results are read visually, so interpretation is subject to individual variation.
Fecal immunochemical tests use monoclonal or polyclonal antibodies to human globulin to detect human blood in stool. These antibodies are not cross-reactive with nonhuman globulin or food-based peroxidases, so dietary restrictions are unnecessary. Because human globulin does not survive passage through the upper GI tract, fecal immunochemical testing targets bleeding from the colon and rectum. Furthermore, only one stool sample is needed. Tests can be read visually or by an automated method that allows standardized interpretation, for better accuracy. The cost is covered by Medicare.
While fecal occult blood tests do not allow colorectal cancer to be prevented, they are less expensive and invasive than colonoscopy and are proved to decrease the rate of death from colon cancer. Fecal immunochemical tests, with their superior sensitivity and compliance, should improve participation in colorectal screening programs and ultimately may reduce mortality rates. Immunochemical testing is now recommended by the US Multi-society Task Force, the US Preventive Services Task Force, and the American College of Gastroenterology. More details about this review, “New fecal occult blood tests may improve adherence and mortality rates,” are posted online at www.ccjm.org/content/78/8/515.long.