S1166 The Usefulness of Screening Colonoscopy in Asymptomatic Hong Kong Chinese Aged Between 40-49 Years

Aim: To determine the prevalence of colorectal adenoma in asymptomatic Hong Kong Chinese 40 to 49 years with and without a first-degree relative with colorectal cancer. Methods: We performed colonoscopy in consecutive asymptomatic subjects 40 to 49 years of age who voluntarily participated in this screening program. Lesions seen during colonoscopy examination were removed. An advanced neoplasm was defined as an adenoma at least 10mm in diameter, with villous histologic features, severe dysplasia, or a cancer. The junction between splenic flexure and descending colon defined proximal and distal location. Results: One thousand and five subjects underwent screening colonoscopy over a twenty eight month period. Of them 1001 (Men 377, Mean age [SD] 44.9 [2.8]) had a complete examination; 690 (68.9%) subjects had no detectable lesions, 177 (17.7%) had tubular adenomas, 109 (10.9%) had hyperplastic polyps and 25 (2.5%) (95 percent confidence interval 1.5% to 3.5%) had advanced neoplasm including 3 invasive cancers. Eighteen of 25 (72%) advanced neoplasms were located in the distal colon. A family history (one first degree relative with colorectal cancer diagnosed below 60 years of age) was present in 216 subjects. The number needed to treat to detect an advanced neoplasm was 40 (95 percent confidence interval 29 to 67). Factors predictive of the presence of any adenoma were male sex (OR 1.47, 95% confidence interval 1.06 to 2.05, p=0.0231) and age (OR 1.08, 95% confidence interval 1.01 to 1.14, p=0.019). Having a first-degree relative with colorectal cancer was not predictive of an advanced neoplasm (OR 1.7, 95% confidence interval 0.7-4.1, p=0.205) Conclusions : In asymptomatic Hong Kong Chinese between 40 to 49 years of age, the incidence of advanced neoplasm was low. The findings of invasive cancers however raise concern over the current screening recommendation.