RESUMO
<p><b>OBJECTIVE</b>To compare the age-specific detection rates of colorectal neoplasms by colonoscopic screening among high-risk population in rural area and to provide evidence for determining the initial age in the colorectal cancer screening.</p><p><b>METHODS</b>The age-specific detection rates of colorectal cancers and adenomas, and the proportion of detected cases in each age group after screening by the optimized sequential colorectal cancer screening program in Jiashan County, Zhejiang Province, were analyzed.</p><p><b>RESULTS</b>Mass screening with the optimized sequential colorectal cancer screening program in Jiashan was conducted and 8867 colonoscopic examinations were performed. A total of 1811 individuals with at least one colorectal neoplastic lesion were found. Among them, there were 92 (1.04%) colorectal cancer patients, 1164 (13.13%) patients with at least one adenoma and 377 (4.25%) patients with at least one advanced adenoma. The detection rate of colorectal neoplastic lesions for the age group 40 - 44 was considerably lower than that in the age group 45 - 49. Hypothetically, to increase the initial age to 45-years for the optimized sequential colorectal cancer screening program would yield a 7.84% increase in the detection rate of total colorectal neoplastic lesions, 13.46% increase in the detection rate of colorectal cancer, 8.76% increase in the detection rate of adenoma, 12.24% increase in the detection rate of advanced adenoma and 19.64% lower in the cost of initial screening, 13.30% lower in the cost of colonoscopic screening.</p><p><b>CONCLUSIONS</b>Among the high-risk population aged 40 to 74, the detection rates of colorectal cancer and adenoma are increasing with the increase of age, the detection rates of colorectal cancer and adenoma as well as proportion of detected cases in the 40 - 44 age group are considerably lower. To increase the initial age to 45 for colorectal cancer screening in rural area of China is reasonable.</p>