A Prospective Study of the Prevalence and Distribution of Colorectal Neoplasia in Asymptomatic Asian Population

Abstract

Background/Aims: With the rapid increase in the incidence of colorectal cancer in some Asian countries, interest in screening test in asymptomatic individuals is increasing. However, few studies on this field have been conducted in Asia. We aim to evaluate the prevalence, distribution and predicting factors of colorectal neoplasia in asymptomatic Asian individuals. Methods: We conducted a prospective, cross-sectional study of 9018 consecutive patients undergoing colonoscopy in 17 centers of 11 Asian cities (Bangkok, Delhi, Guangzhou, Hong Kong, Jakarta, Kuala Lumpur, Manila, Seoul, Singapore, Taipei, Tokyo) between July 2004 and December 2004. Of those, colonoscopic results of 860 asymptomatic screening individuals were analyzed. Advanced neoplasia was defined as adenoma larger than 10 mm in diameter, adenoma with high grade dysplasia, villous adenoma, or invasive cancer. The proximal neoplasm was considered as neoplasia at and proximal to the splenic flexure. Results: The mean age of 860 asymptomatic subjects was 54.4 ± 11.6 years and 471 (54.8%) were male. The overall prevalence of colorectal adenoma, advanced neoplasm, and invasive cancer was 18.5%, 4.5%, and 1.0% respectively. The prevalence of distal, proximal, and synchronous colorectal adenoma (advanced neoplasm) was 8.8% (2.1%), 7.7% (2.0%), and 3.0% (0.3%) respectively. In multivariate logistic regression analysis, male gender (p = 0.021), older age (p = 0.005), and family history of colorectal cancer in the first degree relatives (p = 0.009) were associated with an increased risk of colorectal advanced neoplasia. The ethnicity of Korean and Japanese was associated with an increased risk of colorectal adenoma but not with advanced neoplasia. In analysis comparing the risk of proximal advanced neoplasm in patients with distal adenoma vs those with no distal polyps, the adjusted relative risk was 3.1 (95% CI, 1.1-8.4). In asymptomatic screening subjects with no distal polyps (n = 720), 7.9% and 1.8% of the subjects have adenoma and advanced neoplasia in proximal colon respectively, and in multivariate analysis, first degree relative with history of colorectal cancer was a significant predicting factor for proximal advanced neoplasm (p < 0.021). In addition, 65% (13/20) of patients with proximal advanced neoplasm had no distal polyp, and the proportion of patients with proximal adenoma or advanced neoplasm increased with age. Conclusions: In asymptomatic Asian populations, male gender, older age and family history of colorectal cancer were associated with an increased risk of colorectal neoplasm. Quite a portion of proximal colonic neoplasia was detected with no distal polyp, especially in the elderly.