The prevalence rate and anatomic location of colorectal adenoma and cancer detected by colonoscopy in average-risk individuals aged 40-80 years.

Background: The role of screening colonoscopy for colorectal (CR) neoplasia in average-risk population, remains to be determined.

Objectives: To evaluate the prevalence and anatomic location of CR adenoma and carcinoma and the morbidity of colonoscopy in individuals at average risk for CR cancer (CRC).

Methods: A retrospective prevalence study of subjects aged 40-80 yr, with no cancer-related symptoms, personal or family history of CR neoplasia, who underwent a colonoscopy.

Results: Enrolled were 1,177 persons; 183 aged 40-49 yr (young), 917 aged 50-75 yr, and 77 aged 76-80 yr (elderly). The prevalence of overall CR neoplasia, advanced neoplasia, and cancer was 20.9%, 6.3%, and 1.1%, respectively. In the 50-75 age group, the prevalence of overall adenoma, advanced neoplasia, and cancer was 21.3%, 6.7%, and 1.2%, respectively. Of the 206 neoplasia cases, 21-43% harbored proximal neoplasia beyond the reach of sigmoidoscopy, without distal lesions. Among the elderly, the prevalence of overall adenoma, advanced neoplasia, and cancer reached 26.0%, 14.3%, and 2.6%, respectively. In the young group, 9.8% had overall neoplasia, 1.1% had advanced adenoma, and none had CRC. Procedure-related morbidity rate was 0.1%, with no perforations, bleedings, or mortality.

Conclusions: Screening colonoscopy in average-risk subjects demonstrated a considerable prevalence of CR neoplasia and proximal lesions beyond the reach of sigmoidoscopy. The morbidity rate was negligible. Primary screening colonoscopy should be considered in health programs for the average-risk population, beginning at the age of 50 yr. The significantly high rate of advanced and proximal neoplasia in the elderly, encourages the inclusion of healthy subjects aged 76-80 yr in future prospective studies.