Comparison of CT colonography, colonoscopy, sigmoidoscopy and faecal occult blood tests for the detection of advanced adenoma in an average risk population

Abstract

Background and aims: This prospective trial was designed to compare the performance characteristics of five different screening tests in parallel for the detection of advanced colonic neoplasia: CT colonography (CTC), colonoscopy (OC), flexible sigmoidoscopy (FS), faecal immunochemical stool testing (FIT) and faecal occult blood testing (FOBT). Methods: Average risk adults provided stool specimens for FOBT and FIT, and underwent same-day low-dose 64-multidetector row CTC and OC using segmentally unblinded OC as the standard of reference. Sensitivities and specificities were calculated for each single test, and for combinations of FS and stool tests. CTC radiation exposure was measured, and patient comfort levels and preferences were assessed by questionnaire. Results: 221 adenomas were detected in 307 subjects who completed CTC (mean radiation dose, 4.5 mSv) and OC; 269 patients provided stool samples for both FOBT and FIT. Sensitivities of OC, CTC, FS, FIT and FOBT for advanced colonic neoplasia were 100% (95% CI 88.4% to 100%), 96.7% (82.8% to 99.9%), 83.3% (95% CI 65.3% to 94.4%), 32% (95% CI 14.9% to 53.5) and 20% (95% CI 6.8% to 40.7%), respectively. Combination of FS with FOBT or FIT led to no relevant increase in sensitivity. 12 of 45 advanced adenomas were smaller than 10 mm. 46% of patients preferred CTC and 37% preferred OC (p,0.001). Conclusions: High-resolution and low-dose CTC is feasible for colorectal cancer screening and reaches sensitivities comparable with OC for polyps .5 mm. For patients who refuse full bowel preparation and OC or CTC, FS should be preferred over stool tests. However, in cases where stool tests are performed, FIT should be recommended rather than FOBT.Colorectal cancer is one of the major public health issues in industrialised countries. Most colorectal cancers are thought to originate from benign adenomatous polyps that develop over a period of many years.1 Early detection followed by removal of adenomas has been shown to reduce incidence and colorectal cancer-related mortality.2 3Therefore, screening of the asymptomatic and average risk population is recommended by many organisations and expert panels, and is reimbursed by insurance companies in several countries. 4-7Next to colonoscopy, flexible sigmoidoscopy (FS) and guaiac-based faecal occult blood test (FOBT) are widely applied screening procedures which have been compared prospectively with each other. Colonoscopy has been found to be the screening test with the highest sensitivity and outperforms FS and FOBT which miss a significant number of relevant adenomas. 8 Colonoscopy, however, is not a perfect test in itself, and misses 6-12% of large adenomas. 9-11CT colonography (CTC), also known as virtual colonoscopy, and faecal immunochemical tests (FITs) have been proposed as screening tests for colonic neoplasia.12-14 They have at present not been integrated into screening programmes. Based on recent research, CTC shows heterogeneous results in the detection of colonic polyps: some studies demonstrated high sen...

Risk of cancer in small and diminutive colorectal polyps

“…Our results are consistent with much of the previously published literature [3][4][5][6][7][8][9][10][11][12][13][14][15][20][21][22][23][24][25][26][27] , particularly reports from the last 10 years ( Table 2). As noted earlier, the trends toward decreasing prevalence rates of cancer in small and diminutive polyps may reflect the improved imaging capabilities of colonoscopes, and increasing emphasis on identification of flat lesions which do not increase the risk of cancer compared to polypoid lesions [16][17][18] .…”

“…The overall distribution of polyp sizes in this study suggests that the tendency of endoscopists in our unit is to underestimate polyp size, particularly since the percentage of all polyps < 1 cm in size was comparable to other studies [3][4][5][6][7][8][9][10][11][12][13][14][15][21][22][23][24][25][26][27] , despite our center receiving many referrals for large and complex polypectomies 28 . Further the fraction of polyps ≤ 5 mm and 6-9 mm in size was comparable to or higher than prior studies [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][22][23][24][25][26][27][28][29] .…”

“…Further the fraction of polyps ≤ 5 mm and 6-9 mm in size was comparable to or higher than prior studies [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][22][23][24][25][26][27][28][29] . Any underestimation of polyp size would tend to cause the apparent prevalence of cancer in polyps of different size ranges to increase.…”

“…However, more recent colonoscopic studies found a much lower prevalence [8][9][10][11][12][13][14][15] . These differences may reflect in part the improved potential for polyp identification resulting from progressive improvements in colonoscope imaging.…”

Test Performance of Immunologic Fecal Occult Blood Testing and Sigmoidoscopy Compared with Primary Colonoscopy Screening for Colorectal Advanced Adenomas

“…Test performance of the semiquantitative FIT appears to be superior to that of the guaiac-based FOBTs (7,8), but so far, results of randomized controlled trials on the effects of FIT on CRC mortality are lacking. Although many studies assessed the individual performance of FIT or sigmoidoscopy in various populations, only a few were conducted comparing both methods with colonoscopy as a reference standard in screening populations (9,10). In addition, the impact of age, gender, and location of adenomas on performance of the most commonly used screening tests has not been extensively studied.…”