Controversies in Colorectal Cancer Screening

Abstract

Background: Colorectal cancer (CRC) is one of the most common cancers worldwide and a good candidate for screening programmes. However, there is controversy concerning which of the available screening tests should be used. Summary: There is general agreement that screening for CRC in the asymptomatic population should begin at the age of 50. Several different screening methods are available which can be separated into those that mainly detect cancers: faecal occult blood tests [guaiac (FOBT) and immunochemical (FIT)], genetic stool tests, blood tests and the M2-pyruvate kinase (M2-PK) test. Methods that detect cancers and polyps are colonoscopy, sigmoidoscopy, CT-colonography (CT-C) and colon capsule endoscopy. The only tests for which a reduction in CRC mortality compared to no screening have been proven in randomized trials are FOBT and sigmoidoscopy. Several trials suggest that FIT are superior to FOBT in terms of detection rates of cancers and advanced adenomas and possibly compliance. There is indirect evidence suggesting efficacy of colonoscopy as a screening test. The role of CT-C is controversial. There is data suggesting a good sensitivity for neoplasia >9 mm with a lower sensitivity for smaller neoplasia. However, radiation exposure is considered a major limitation in some countries. Unresolved questions include the lesion cut-off for referral to colonoscopy and work-up of extracolonic findings. For other methods, like genetic stool testing using newer markers, blood tests, capsule endoscopy and M2-PK, there is currently insufficient data on screening of the asymptomatic population. Key Messages: Colorectal screening is recommended and should be performed in the form of an organized programme. If detection of early-stage cancers is the aim of a screening programme, FIT seem to be superior to FOBT. If detection and removal of adenomas is the aim of a screening programme, endoscopic methods seem to be good alternatives. Sigmoidoscopy is easier to perform but will likely only have an effect on distal cancers. Colonoscopy is more invasive but enables inspection of the whole colon. The role of CT-C, capsule endoscopy, genetic stool tests, blood tests and M2-PK is currently unknown.

A Pilot Study of Fluorescent Imaging of Colorectal Tumors Using a γ-Glutamyl-Transpeptidase-Activatable Fluorescent Probe

“…Currently, screening colonoscopy is widely accepted as the gold standard for colorectal cancer detection [1,2,3]. Indeed, early detection of polyps and their subsequent endoscopic removal are the best ways to reduce colorectal cancer mortality [1,2,3].…”

“…Indeed, early detection of polyps and their subsequent endoscopic removal are the best ways to reduce colorectal cancer mortality [1,2,3]. Various image-enhanced endoscopy techniques, such as chromoendoscopy [4,5], narrow-band imaging [6,7], autofluorescence imaging [8] and confocal laser endomicroscopy [9], have improved the detection and characterization of colorectal neoplasms.…”

Impact of screening colonoscopy on outcomes in colorectal cancer

“…In general, a high detection rate (≥90%) for polyps >9 mm has been reported, while the detection rate for polyps >5 mm was lower (78-91%) (21,22,24). The referral rate for colonoscopy in the studies varied between 7.5 and 17.3% for a cutoff of 10 mm and 17.5 and 29.7% for a cutoff polyp size of >5 mm, therefore, it is still now controversial what the ideal threshold for colonoscopy referral is (25). In a randomized trial comparing CT-colonography and colonoscopy for primary screening, the participation rate of CT-colonography was significantly higher (34 vs. 22%, P < 0.0001), whereas the detection rate of advanced neoplasia was higher with colonoscopy (6.1 vs. 8.7%, P = 0.02) (19).…”

Molecular pathology of colorectal cancer

“…The standard approach for these screening programs is fecal occult blood testing (FOBT), in order to identify a more limited population qualifying for colonoscopy in case of a positive FOBT. Fecal occult blood testing is relatively sensitive but lacks specificity [34]. A variety of molecular approaches are under investigation to develop more specific tests.…”