Follow-up study on screening for early colorectal cancer in Shipai, Dongguan City, China

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Objective: To examine follow-up data of different subgroups in order to further evaluate the performance and practical value of community colorectal cancer screening by detection of stool methylation syndecan-2 gene (mSDC2) among residents of Shipai Town, Dongguan City. Methods: This was an observational study. From May 2021 to February 2022, the Shipai Town government of Dongguan City completed screening for colorectal cancer by detection of stool mSDC2 in 10,708 residents from 18 villages who had met the initial screening criteria and been selected using whole population sampling. From May 2022 to February 2023, the research group conducted follow-up of participants about one year after the initial screening. Residents in the gray zone according to the initial screening were followed up by colonoscopy. Additionally, 1,000 residents with negative results on the initial screening were randomly sampled to undergo colonoscopy. Stool mSDC2 detection was performed again on residents who had had positive results on the initial screening, and colonoscopy was performed on those who again tested positive. Compliance with colonoscopy and detection of gastrointestinal lesions during follow-up were assessed in different subgroups. Results: Of the 438 residents in the gray zone on the initial screening, 155 underwent colonoscopy follow-up (colonoscopy compliance rate 35.4% [155/438]). These colonoscopies revealed that 27 (17.4%) of the participants had gastrointestinal lesions, including advanced adenomas in 22 cases (14.2%) and non-adenomatous polyps in two cases (3.2%). No colorectal carcinomas was identified. Of the 1, 000 randomly sampled residents with negative results on initial screening, 286 underwent colonoscopy follow-up (colonoscopy compliance rate 28.6% [286/1000]), These colonoscopies revealed that 11 (3.8%)of these individuals had gastrointestinal lesions, including three advanced adenomas (1.0%), five non-advanced adenomas (1.7%), one serrated adenoma or polyp (0.3%), and two non-adenomatous polyps (0.7%), but no colorectal carcinomas. Of the 821 residents who tested positive in the initial screening, 511 again underwent stool mSDC2 detection one year later (follow-up rate 62.2% [511/821]). Of these participants, 66 tested positive again (rate of 12.9% [66/511]), 39 (7.6%) of them in the gray zone, whereas 406(79.5%) tested negative. Forty-seven of the residents with positive results underwent colonoscopy (colonoscopy compliance rate 71.2% [47/66]), which revealed 36 (76.6%) gastrointestinal lesions, including 10 advanced adenomas (21.3%), nine non-advanced adenomas (19.1%) and 17 non-adenomatous polyps (36.2%). Conclusion: Stool mSDC2 detection performs well as a screening tool. In our study, colorectal cancer or precancerous lesions were extremely rare in participants who tested negative on the initial screening. However, some of the participants who tested in the gray zone on initial screening had precancerous colorectal lesions, particularly advanced adenomas, which would have been missed without follow-up colonoscopy. Of note, stool mSDC2 detection has good follow-up value in individuals who test positive on initial screening.