Abstract
Background and Methods. The role of colonoscopy in
screening for colorectal cancer is uncertain. At 13 Veterans Affairs medical
centers, we performed colonoscopy to determine the prevalence and location
of advanced colonic neoplasms and the risk of advanced proximal neoplasia in
asymptomatic patients (age range, 50 to 75 years) with or without distal
neoplasia. Advanced colonic neoplasia was defined as an adenoma that was 10
mm or more in diameter, a villous adenoma, an adenoma with high-grade
dysplasia, or invasive cancer. In patients with more than one neoplastic
lesion, classification was based on the most advanced lesion.
Results. Of 17,732 patients screened for enrollment, 3196
were enrolled; 3121 of the enrolled patients (97.7 percent) underwent
complete examination of the colon. The mean age of the patients was 62.9
years, and 96.8 percent were men. Colonoscopic examination showed one or
more neoplastic lesions in 37.5 percent of the patients, an adenoma with a
diameter of at least 10 mm or a villous adenoma in 7.9 percent, an adenoma
with high-grade dysplasia in 1.6 percent, and invasive cancer in 1.0
percent. Of the 1765 patients with no polyps in the portion of the colon
that was distal to the splenic flexure, 48 (2.7 percent) had advanced
proximal neoplasms. Patients with large adenomas (greater than or equal to
10 mm) or small adenomas (<10 mm) in the distal colon were more likely to
have advanced proximal neoplasia than were patients with no distal adenomas
(odds ratios, 3.4 [95 percent confidence interval, 1.8 to 6.5] and 2.6 [95
percent confidence interval, 1.7 to 4.1], respectively). However, 52 percent
of the 128 patients with advanced proximal neoplasia had no distal adenomas.
Conclusions. Colonoscopic screening can detect advanced
colonic neoplasms in asymptomatic adults. Many of these neoplasms would not
be detected with sigmoidoscopy. (N Engl J Med 2000;343:162-8.)
