By Neil Osterweil , MedPage Today Staff Writer. Reviewed by Robert Jasmer, MD; Assistant Professor of Medicine, University of California, San Francisco
Review: OKAYAMA, Japan, Aug. 23-Fecal immunochemical tests (FIT) are an improved approach to fecal occult blood tests for detecting possible colorectal cancer, according to researchers here.
Nevertheless, FIT has a relatively low sensitivity and is better at picking up some tumors than others, according to Jun Kato, M.D., of Okayama University and colleagues reported in the August issue of Gastroenterology.
In a study comparing FIT results with findings from colonoscopy, Dr. Kato’s group found that FIT picked up slightly more than one-fourth of advanced cancers and two-thirds of invasive cancers. In addition, the test detected about twice as many cancers when the lesions occurred in the distal colon rather than the proximal colon.
Gastroenterologist James E. Allison, M.D., of the University of California at San Francisco, who wrote an editorial accompanying the study, called FIT a more sensitive and specific test for colorectal cancers than standard fecal occult blood tests (FOBT). What’s more, he added, FIT screening results are not affected by medications or diet, meaning a reduced likelihood of false positive results if the patient has recently consumed beef.
FIT kits, which have been approved for reimbursement by Medicare, use antibodies to human globin expressed in colorectal bleeding. Unlike standard guaiac-based tests such as Hemoccult II, the results are not affected by the presence in the diet of vitamin C, animal blood, or foods containing peroxidase (e.g., radishes, turnips, or broccoli).
“If, as it appears, the FIT has better performance characteristics than the [guaiac test], that is compelling evidence for recommending its use as the FOBT of choice in colon cancer screening programs,” Dr. Allison wrote.
In their study, Dr. Kato and colleagues looked at the sensitivity of FIT compared with colonoscopy in 21,805 asymptomatic adults. The patients underwent simultaneous FIT and colonoscopy.
The investigators found that FIT was positive in 1,231 cases (5.6%). The sensitivity was 27.1% for advanced neoplasias, and 65.8% for invasive cancer. As the cancer stage increased in severity, so did the sensitivity of the test, at 50.0% for Dukes’ stage A, 70.0% for Dukes’ stage B, and 78.3% for Dukes’ stages C or D.
The sensitivity for detecting advanced neoplasia at the proximal colon was 16.3%, compared with 30.7% for disease in the distal colon (P = 0.00007).
“Although the screening of asymptomatic patients with immunochemical FOBT can identify patients with colorectal neoplasia to a certain extent, the sensitivity is relatively low and different according to the tumor location,” the Japanese team wrote. “Therefore, programmatic and repeated screening by immunochemical FOBT may be necessary to increase sensitivity for colorectal cancer detection.”
Although it’s not perfect, FIT is still better than standard FOBT, Dr. Allison argues.
“The fecal immunochemical tests (FIT) address many of the weaknesses of the [guaiac test],” Dr. Allison wrote. “They have superior sensitivity and specificity. The application sensitivities for cancer are good (66% to 82%) but for polyps or more than 1 cm they are more modest; however, the use of a program of fecal occult blood test (FOBT) screening (in which screening is performed yearly or every other year) may result in a cumulative sensitivity of the program that is competitive with a program of a more sensitive test performed less frequently.”
He commented that a program combining FIT-based FOBT plus sigmoidoscopy could be comparably effective to a program of colonoscopy screening every 10 years, because of the improved sensitivity of FIT-based tests.
“The suggestion of some experts that FOBT screening should be seriously considered by physicians, patients, and policy makers should now make the case for FOBT even stronger,” he wrote.
The above is for general informational purposes only. Always consult your physician regarding specific medical issues and call Hatzalah or your local ambulance service in the event of an emergency.