Colorectal Cancer Screening (PDQ®): Screening - Health Professional Information [NCI] - Evidence of Benefit
Table 3. Randomized Controlled Screening Trials: Fecal Occult Blood Testing continued...
A study of colonoscopy in women compared the yield of sigmoidoscopy versus colonoscopy. Among 1,463 women, cancer was found in one woman and advanced colonic neoplasia in 72 women or 4.9% (about one-half the prevalence compared with men). The authors focused, however, on RR (i.e., RR of missing an advanced neoplasm) as the outcome, instead of absolute risk of such neoplasms, which is substantially lower in women. In addition, the natural history of advanced neoplasia is not known, so its importance as an outcome in studies of detection is not clear.
Analysis of data from a colonoscopy-based screening program in Warsaw, Poland demonstrated higher rates of advanced neoplasia in men than in women. The predominant age range of participants was 50 to 66 years. Of the 43,042 participants aged 50 to 66 years, advanced neoplasia was detected in 5.9% (5.7% among women with a family history of CRC, 4.3% among women without a family history of CRC, 12.2% among men with a family history of CRC, and 8.0% among men without a family history of CRC). Clinically significant complications requiring medical intervention were rare (0.1%) consisting of five perforations, 13 episodes of bleeding, 22 cardiovascular events, and 11 other events over the entire population of 50,148 screened persons. There were no deaths; however, the author reported that collection of 30-day complications data was not systematic; therefore, the data may not be reliable.
Detection rates in colonoscopy screening vary with the rate at which the endoscopist examines the colon while withdrawing the scope. Detection rates among gastroenterologists (mean number of lesions per patient screened, 0.10–1.05; range of the percentage of patients with adenomas, 9.4%–23.7%) and the times to withdraw (3.1–16.8 minutes for procedures not including polyp removal). Examiners whose mean withdrawal time was 6 minutes or more had higher detection rates than those with mean withdrawal times of less than 6 minutes (28.3% vs. 11.8%; P < .001 for any neoplasia) and (6.4% vs. 2.6%; P < .005 for advanced neoplasia). Overall detection rate of adenomas and cancer may be affected by how thoroughly endoscopists search for flat adenomas and flat cancer. While the phenomenon of flat neoplasms has been appreciated for years in Japan, it has more recently been described in the United States. In a study in which endoscopists used high-resolution white-light endoscopes, flat or nonpolypoid lesions were found to account for only 11% of all superficial colon lesions, but they were about 9.8 times as likely to contain cancer (in situ neoplasia or invasive cancer) compared with polypoid lesions. However, because the definition of flat or nonpolypoid was height less than one-half of the diameter, it is likely that many lesions classified as nonpolypoid in this study would be routinely found and described by U.S. endoscopists as sessile. At the same time, the existence of very flat or depressed lesions (depressed lesions are very uncommon but are highly likely to contain cancer) means that endoscopists will want to pay increasing attention to this problem. Flat lesions may play a role in the phenomenon of missed cancers.