Effect of Cotinine-Verified Change in Smoking Status on Risk of Metachronous Colorectal Neoplasia After Polypectomy

Background & Aims: Previous assessments of colorectal neoplasia (CRN) recurrence after polypectomy used self-report to determine smoking status. We evaluated the association between change in smoking status and metachronous CRN risk after polypectomy using cotinine level in urine to determine tobacco exposure. Methods: We performed a retrospective study of participants in the Kangbuk Samsung Health Study in Korea who underwent a screening colonoscopy examination and measurement of cotinine in urine samples. Our analysis included 4762 patients who had 1 or more adenomas detected in an index colonoscopy performed between January 2010 and December 2014, and underwent a surveillance colonoscopy, 6 or more months later, until December 2017. Results: Patients were classified into 4 groups based on the change in cotinine-verified smoking status from index to follow-up colonoscopy (mean interval, 3.2 ± 1.3 y), as follows: remained nonsmokers (n = 2962; group 1), smokers changed to nonsmokers (n = 600; group 2), nonsmokers changed to smokers (n = 138; group 3), and remained smokers (n = 1062; group 4). After adjustment for confounding factors, group 4 had a significantly higher risk of metachronous CRN than group 1 (hazard ratio [HR], 1.54; 95% CI, 1.36–1.73) and group 2 (HR, 1.63; 95% CI, 1.39–1.99). Group 4 also had a higher risk of metachronous advanced CRN than group 1 (HR, 2.84; 95% CI, 1.79–4.53) and group 2 (HR, 2.10; 95% CI, 1.13–3.89). Group 3 had a higher risk of metachronous CRN than group 1 (HR, 1.50; 95% CI, 1.14–1.97) and group 2 (HR, 1.62; 95% CI, 1.20–2.20). Conclusions: In a retrospective study of individuals with at least 1 adenoma, we found that cotinine-verified changes in smoking status between index and follow-up colonoscopy are associated with a risk of metachronous CRN. Helping patients quit smoking is important for effective prevention of colorectal cancer.