[Study on the application value of fecal SDC2 gene methylation detection in colorectal cancer screening of urban residents in Zengcheng District in Guangzhou City].

Objective: To investigate the application value of fecal Syndecan-2 (SDC2) gene methylated SDC2 (mSDC2) detection in colorectal cancer (CRC) screening among urban residents in Guangzhou City. Methods: A cross-sectional study was conducted in Shitan Town, Zengcheng District, Guangzhou City from July to December 2022. A community-based screening program for CRC was conducted among residents aged 40-74 years old. mSDC2 detection was employed in the participants, and those with positive results should be recommended to receive colonoscopy examination. The positive rate of mSDC2 detection, colonoscopy compliance rate, detection rate of intestinal lesions and clinicopathological characteristics were observed. The relationship between cycle threshold (CT) value of mSDC2 and intestinal lesions was explored. Further, the cost-effectiveness of screening was evaluated. Results: A total of 8 189 fecal samples were collected from 8 877 participants with the recovery rate of 92.25%. 8 048 qualified samples were enrolled in this study, consisted of 3 182 males (39.54%) and 4 866 females (60.46%), with the average age of 56 years old (40-74 years). The positive rate of mSDC2 detection was 7.99% (643/8 048), and the compliance rate of colonoscopy was 73.10% (470/643). 20 cases (4.25%) of colorectal cancer, 109 cases (23.19%) of advanced adenoma, 145 cases (30.85%) of non-advanced adenoma, 79 cases (16.81%) of polyps were detected. The detection rate of intestinal lesions was 75.11% and indicated significant differences in gender and age. 20 CRCs included 15 of stage 0-I, 4 of stage Ⅱ-Ⅲ and 1 of unknown stage. The CT value of mSDC2 was negatively correlated with the proportion of advanced colorectal neoplasms (χ2=16.063, P<0.001). The total cost of the screening was 4.339 5 million yuan, the screening benefit was 28.506 2 million yuan, and the benefit-cost ratio was 6.57. Conclusion: The CRC screening strategy of fecal mSDC2 detection combined with colonoscopy has high colonoscopy compliance and detection rate of intestinal lesions, which is conducive to the detection of early CRCs, and has good cost-effectiveness. This study suggests that this method may be applied to the general CRC screening in China and contribute to the prevention of CRC. The CT value of mSDC2 may have a certain suggestion on the malignant degree of intestinal tumors.