Noninvasive Screening Tests for Colorectal Cancer

Digestive Diseases (Impact Factor: 2.18). 11/2012; 30(s2):16-26. DOI: 10.1159/000341884


Identifying an accurate, reliable, affordable, and acceptable noninvasive screening test for colorectal cancer (CRC) would greatly facilitate population screening.

Published literature from 2000 through February 2012 on noninvasive CRC screening tests was identified, reviewed, and summarized.

The highest quality evidence for noninvasive screening exists for guaiac-based fecal occult blood tests (gFOBTs), for which the CRC-specific incidence and mortality reductions are modest. Fecal immunochemical tests (FITs) offer better sensitivity and comparable specificity. Cross-sectional studies comparing gFOBTs and FITs suggest that FITs provide higher detection of advanced neoplasia. Modeling studies favor FITs over gFOBTs with respect to effectiveness and cost-effectiveness. A myriad of studies report the performance of fecal-based and blood-based genetic and protein-based biomarkers; the studies differ in patient population assembled, marker selection, and assay methods. Several markers and panels of markers are promising, although nearly all studies focus on new markers and/or assay methods on small sets of referred patients rather than validating markers using optimal assays in a screening setting.

In the absence of long-term randomized trials, adoption of the noninvasive tests will require cross-sectional data on test characteristics obtained from the screening setting, where CRC prevalence is low and the full spectrum of colorectal findings exists, along with estimates of cumulative risks, benefits, and cost-effectiveness. Test adoption will ultimately depend on test characteristics, availability, affordability, and user appeal. There is no noninvasive substitute for the currently recommended screening tests. FITs should replace gFOBTs wherever gFOBTs are used for screening.

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    ABSTRACT: Background Colorectal cancer (CRC) is a leading cause of cancer morbidity and mortality. A well-defined precursor lesion (adenoma) and a long preclinical course make CRC a candidate for screening. This paper reviews the current evidence for the most important tests that are widely used or under development for population-based screening.Material and methodsIn this narrative review, we scrutinized all papers we have been aware of, and carried out searches in PubMed and Cochrane library for relevant literature.ResultsTwo screening methods have been shown to reduce CRC mortality in randomised trials: repetitive faecal occult blood testing (FOBT) reduces CRC mortality by 16%; once-only flexible sigmoidoscopy (FS) by 28%. FS screening also reduces CRC incidence (by 18%), FOBT does not. Colonoscopy screening has a potentially larger effect on CRC incidence and mortality, but randomised trials are lacking. New screening methods are on the horizon but need to be tested in large clinical trials before implementation in population screening.ConclusionsFS screening reduces CRC incidence and CRC mortality by removal of adenomas; FOBT reduces CRC mortality by early detection of cancer. Several other tests are available, but none has been evaluated in randomised trials. Screening strategies differ considerably across countries.
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    ABSTRACT: There is increasing evidence that faecal immunochemical tests (FITs) for haemoglobin offer a number of advantages over traditional guaiac based faecal occult blood tests (gFOBTs). However, evidence on diagnostic performance from direct comparisons with colonoscopy findings in all participants in the average risk population is still sparse. We aimed for a head-to-head comparison of three quantitative FITs with a gFOBT among participants of the German screening colonoscopy programme. Pre-colonoscopy stool samples and colonoscopy reports were obtained from 2235 participants of screening colonoscopy in 2005-2009. To enhance comparability of diagnostic performance of the various tests, we assessed sensitivity, specificity, predictive values and likelihood ratios of FITs after adjusting the FIT cut-off haemoglobin (Hb) concentrations in such a way that FIT positivity rates equalled the positivity rate of the gFOBT. Colorectal cancer, advanced adenomas and other adenomas were found in 15 (0.7%), 207 (9.3%) and 398 (17.8%) participants. The gFOBT was positive in 111 (5.0%) participants, with sensitivities (specificities) for detecting colorectal cancer, any advanced neoplasm or any neoplasm of 33.3% (95.2%), 8.6% (95.4%) and 5.5% (95.2%). At the same positivity rate, all three FITs outperformed the gFOBT in all indicators. In particular, all sensitivities of FITs were approximately two to three times higher at increased levels of specificity. All differences were statistically significant, except for some of the performance indicators for colorectal cancer. In conclusion, FITs can detect much larger proportions of colorectal neoplasms even if their cut-offs are set to levels that ensure equally low positivity rates as gFOBT.
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