According to the results of a study published in the Annals of Internal Medicine, the newer type of fecal occult blood test (FOBT) known as an immunochemical FOBT performs better than older approaches to FOBT in the detection of colorectal cancer and colorectal polyps.

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-based FOBT provided a simple and inexpensive screening test, but had limited accuracy.

In response to the limitations of the guaiac-based FOBT, researchers have developed a test known as an immunochemical FOBT. This test is more specific than the guaiac-based test (it produces fewer false-positive results), and certain types of immunochemical FOBT may also be more sensitive (better able to detect cancers and advanced polyps).

In the current study, researchers in Israel compared the results of a quantitative immunochemical FOBT to the results of colonoscopy. A quantitative test provides information about the actual amount of blood in the stool sample, rather than simply providing results as positive or negative. Use of a quantitative test allows physicians to establish their own criteria for when a patient should be referred for additional testing.

The study evaluated 1,000 individuals who were scheduled to undergo colonoscopy. Some of the individuals were receiving colonoscopy for routine screening, and some were undergoing colonoscopy for evaluation of symptoms. All study participants collected three stool samples prior to undergoing colonoscopy.

• During colonoscopy, cancer was identified in 17 study participants, and advanced colorectal polyps were identified in 74 study participants.
• Among the study participants with cancer or advanced polyps, the immunochemical FOBT correctly classified 67% as positive.
• Among the study participants without cancer or advanced polyps, the immunochemical FOBT correctly classified 91% as negative.

The researchers conclude that the quantitative immunochemical FOBT evaluated by this study performed well in the detection of colorectal cancer and advanced colorectal polyps. Because the study included many patients at particularly high-risk of colorectal cancer, it’s uncertain how the test will perform in the general population.

Reference: Levi A, Rozen P, Hazazi R et al. A quantitative immunochemical fecal occult blood test for colorectal neoplasia. Annals of Internal Medicine. 2007;146:244-255.

Related News:  Patients Prefer Conventional Colonoscopy (9/5/2006)

Copyright Colon Cancer Information Center on CancerConsultants.com

Copyright Rectal Cancer Information Center on CancerConsultants.com