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FIT may improve colorectal cancer detection, reduce mortality
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The receipt of fecal immunochemical testing for colorectal cancer could lead to a significant reduction in disease-related mortality, according to the results of a prospective analysis.
However, confirmation of these findings requires an extended follow-up period to observe the long-term impact of fecal immunochemical testing, according to the researchers.
“Fecal immunochemical testing (FIT) has advantages over guaiac fecal occult blood test (gFOBT) screening in several aspects,” Shu-Ti Chiu, PhD, of the Institute of Public Health at the National Yang-Ming University in Taipei, Taiwan, and colleagues wrote. “Studies comparing gFOBT and FIT in screening populations have shown that the former has higher sensitivity for both invasive cancers and advanced adenomas with comparable specificity. This is of utmost importance because the early detection of neoplasms is the key to obtaining a large survival benefit through a cancer screening program.”
Researchers had not previously conducted a large, population-based study of the effectiveness of FIT on colorectal cancer mortality reduction, according to study background.
The Taiwanese government implemented a nationwide colorectal cancer screening program in 2004 that included biennial FIT screening. However, the government staggered countrywide implementation due to budgetary restrictions and clinical availability.
Chiu and colleagues identified 5,417,699 Taiwanese residents aged 50 to 69 years eligible for biennial FIT screening. They designed a prospective cohort study that categorized participants who underwent between one and three rounds of FIT (n = 1,160,895) as the exposed cohort and the remaining eligible population as the unexposed cohort.
Clinicians referred patients with positive FIT screening results for a total colonoscopy or sigmoidoscopy with barium enema for a confirmatory diagnosis.
Maximum follow-up was 6 years.
Overall, 21.4% of eligible Taiwanese residents underwent screening between 2004 and 2009, with 28.3% (n = 329,042) of participants obtaining recommended repeat screenings.
Researchers observed 46,963 positive FIT results at the first screening. Eighty percent (n = 37,585) of patients who tested positive at the first screening and 88% (n = 11,026) of patients who tested positive at a subsequent screening underwent a confirmatory procedure, with 85.5% undergoing colonoscopy.
Confirmatory diagnostic procedures identified 19,398 cases of colorectal adenoma (14,834 from first screening), 5,500 cases of advanced adenomas (4,284 from first screening) and 2,805 invasive cancers (2,304 from first screening). FIT exhibited a positive predictive value of 39.5% for adenoma, 11.7% for advanced adenoma and 6.1% for invasive cancers.
First-round screening resulted in the detection of 16 adenomas per 1,000 screened individuals, 4.6 advanced adenomas per 1,000 screened individuals and 2.5 invasive cancers per 1,000 individuals. Subsequent screening rounds detected 15.6 adenomas, 4.2 advanced adenomas and 1.7 invasive cancers per 1,000 individuals.
FIT screening yielded a 62% effectiveness of mortality reduction in the screened cohort compared with the unscreened cohort (RR = 0.38; 95% CI, 0.35-0.42). Among the 21.4% of eligible participants who underwent FIT screening, researchers observed a significant 10% reduction in disease-related mortality (RR = 0.9; 95% CI, 0.84-0.95).
The researchers acknowledged limitations of their study, including the gradual expansion of the screening program and the inability to ascertain which individuals refused or were unavailable for FIT screening. Further, the budgetary restrictions that led to the staggered screening availability likely contributed to the relatively low screening rate observed in 2009.
“FIT is a feasible and effective test for use in population screening programs,” Chiu and colleagues concluded. “However, continued follow-up of this large cohort is required to assess the true long-term effect of FIT screening if more of the population is covered in a continuing nationwide screening program.”
These results do not account for potential false–negative test results, Grace Clarke Hillyer, EdD, MPH, of the department of epidemiology at Columbia University’s Mailman School of Public Health, and Alfred I. Neugut, MD, PhD, of the Herbert Irving Comprehensive Cancer Center at Columbia University, wrote in an accompanying editorial.
“[An] issue … that typically receives little attention when population-based FIT screening programs are being discussed is the rate of false–negative tests,” Hillyer and Neugut wrote. “A negative FIT result often confers a sense of reassurance regarding risk and may result in longer intervals between screening rounds and thus delayed detection of advanced lesions and poorer health outcomes.”
Because FIT screening will likely remain a frequent option for colorectal cancer testing, researchers must better understand its efficacy, Hillyer and Neugut concluded.
“Cost and simplicity will keep FIT as a major player in the colorectal cancer screening arena for some years to come,” they wrote. “An appreciation of its performance characteristics is critical to being able to decide its role in various scenarios with respect to other screening modalities.” – by Cameron Kelsall
Disclosure: The researchers report no relevant financial disclosures.
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