Colorectal Cancer Screening (PDQ®): Screening - Health Professional Information [NCI] - Evidence of Benefit
Table 3. Randomized Controlled Screening Trials: Fecal Occult Blood Testing continued...
In 2,885 veterans (97% male; mean age 63 years), the prevalence of advanced adenoma at colonoscopy was 10.6%. It was estimated that combined screening with one-time FOBT and sigmoidoscopy would detect 75.8% (95% CI, 71.0%–80.6%) of advanced neoplasms. Examination of the rectum and sigmoid colon during colonoscopy was defined as a surrogate for sigmoidoscopy. This represented a small but statistically insignificant increase in the rate of detection of advanced neoplasia when compared with FS alone (70.3%; 95% CI, 65.2%–75.4%). The latter result could be achieved assuming that all patients with an adenoma in the distal colon undergo complete colonoscopy. Advanced neoplasia was defined as a lesion measuring at least 10 mm in diameter, containing 25% or more villous histology, high-grade dysplasia, or invasive cancer. One-time use of FOBT differs from the annual or biennial application reported in those studies summarized in Table 1.
A study of 21,794 asymptomatic persons (72% were men) who had both colonoscopy and fecal immunochemical testing (FIT) for occult blood compared the detection of right-sided cancers as triggered by different test results. FIT alone resulted in a sensitivity of 58.3% and a specificity of 94.5% for proximal cancer diagnosis. FIT plus the finding of advanced neoplasia in the rectosigmoid colon yielded a sensitivity of 62.5% and a specificity of 93%. Thus, in this trial, the addition of sigmoidoscopy to FIT did not substantially improve the detection of right-sided colon cancers, compared with FIT alone.
The NORCCAP once-only screening study randomly assigned 20,780 men and women, aged 50 to 64 years, to FS only or a combination of FS and FOBT with FlexSure OBT. A positive FS was defined as a finding of any neoplasia or any polyp at least 10 mm. A positive FS or FOBT qualified for colonoscopy. Attendance in this study was 65%. Forty-one cases of CRC were detected (0.3% of screened individuals). Adenomas were found in 2,208 participants (17%), and 545 (4.2%) had high-risk adenomas. There was no difference in diagnosis yield between the FS only and the FS and FOBT groups regarding CRC or high-risk adenoma. There were no serious complications after FS, but there were six perforations after therapeutic colonoscopy (1:336).
As part of the National Polyp Study, colonoscopic examination and barium enema were compared in paired surveillance examinations in those who had undergone a prior colonoscopic polypectomy. The proportion of examinations in which adenomatous polyps were detected by barium enema was related to the size of the adenoma (P = .009); the rate was 32% for colonoscopic examinations in which the largest adenomas detected were no larger than 5 mm, 53% for those in which the largest adenomas detected were 6 mm to 10 mm, and 48% for those in which the largest adenomas detected were larger than 10 mm. In patients who have undergone colonoscopic polypectomy, colonoscopic examination is a more sensitive method of surveillance than double-contrast barium enema.