Prevalence of Colonic Lesions After a Negative Screening Colonoscopy in a Population with Rapidly Rising Colorectal Cancer Incidence: A Prospective Multi-Center Analysis

Abstract

Background: Colorectal cancer (CRC) incidence is rapidly rising in Hong Kong. Limited evidence exists to guide the optimal frequency of repeat endoscopic examination for CRC screening after a negative colonoscopy. Despite a decrease in risk was observed for ten years after a negative colonoscopy, CRC was detected in a minority after an initial negative colonoscopy and the prevalence was unknown. Aim: to identify the prevalence of colonic lesions after an initial negative screening colonoscopy. Methods: Patients with an initial negative colonoscopy done for screening, abdominal pain, or altered bowel habit at 5 to 7 years ago, from four regional hospitals in Hong Kong, were invited to have a second colonoscopy. Indications and results for those who had a colonoscopy repeated prior to this study were ascertained. The cause of death for the deceased was identified either through the computer registry or from history by the relatives. Results: There were 406 patients with an initial negative colonoscopy. 11 patients had colonoscopy repeated before this study for various symptoms. 143 patients were available for the second colonoscopy, 28.6% (41) had colonic polyps, 4% (6) of them were advanced lesion, including one intramucosal adenocarcinoma at sigmoid colon. 63 patients died during this period, including one died of CRC at the ascending colon. The rest of patients either refused the examination or we had loss their contact. Conclusion: Four percent of the patients developed advanced colonic lesion after an initial negative colonoscopy at 5 to 7 years. These advanced lesions might have or have already evolved into malignancy if the screening interval was 10 years. The 10-year interval for an initial negative screening colonoscopy may not be applicable to a population with rapidly rising CRC incidence.