Fecal Immunochemical Test Detects High Percentage of Colon Cancers
by C.H. Weaver M.D.
According to the results of a study published in the Journal of the National Cancer Institute, use of a newer type of fecal occult blood test known as a fecal immunochemical test detected a high percentage of left-sided colorectal cancers (cancers that develop in the last part of the colon or the rectum).
Colorectal cancer is the second leading cause of cancer-related deaths in the U.S. The disease develops in the large intestine, which includes the colon (the longest part of the large intestine) and the rectum (the last several inches).
Because cure rates are high when colorectal cancer is detected and treated early and fall dramatically once the cancer has spread, researchers have been evaluating novel screening methods that will offer higher accuracy and encourage more patient compliance. Currently, it is recommended that people 50 years of age or older and those at a high risk for colorectal cancer are screened for the disease. Screening methods include testing for blood in the stool (fecal occult blood test [FOBT]), sigmoidoscopy, and colonoscopy.
While colonoscopy allows for the most complete detection of colorectal cancers and precancerous colorectal polyps, the test is invasive and may discourage some individuals from being screened for colorectal cancer. On the other hand, the traditional guaiac FOBT provides a simple and inexpensive screening test but has limited accuracy.
In response to the limitations of the guaiac FOBT, researchers have developed a newer type of FOBT known as a fecal immunochemical test. This test is more specific than the guaiac test (it produces fewer false-positive results), and certain types of fecal immunochemical tests may also be more sensitive (better able to detect cancers and advanced polyps).
To evaluate the performance of two types of FOBT-a sensitive guaiac test and a fecal immunochemical test-researchers conducted a study among 5,841 people at average risk of colorectal cancer. Study participants who tested positive on either FOBT received a colonoscopy. Study participants who tested negative received a sigmoidoscopy. Because a sigmoidoscopy only evaluates the last part of the colon (the part of the colon on the left side of the body) the researchers were only able to draw conclusions about the ability of the tests to detect left-sided colorectal cancer.
- The fecal immunochemical test detected 82% of the left-sided colorectal cancers and the sensitive guaiac FOBT detected 64%.
- The fecal immunochemical test detected 30% of advanced adenomas (a precancerous growth) and the sensitive guaiac FOBT detected 41%. It’s unclear why the guaiac test was better able to detect advanced adenomas than the FIT.
- The fecal immunochemical test had higher specificity than the sensitive guaiac FOBT. This means that the fecal immunochemical test produced fewer false-positive test results.
The researchers concluded that the fecal immunochemical test performed well in detecting left-sided colorectal cancer, and may be a useful replacement for the guaiac fecal occult blood test.
Reference: Allison JE, Sakoda LC, Levin TR et al. Screening for colorectal neoplasms with new fecal occult blood tests: update on performance characteristics. Journal of the National Cancer Institute. 2007;99:1462-70.
Related News:Immunochemical FOBT Aids in Detection of Colorectal Cancer and Colorectal Polyps(3/8/2007)
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