Association of smoking and flat adenomas: results from an asymptomatic population screened with a high-definition colonoscope

Background Flat adenomas represent a morphologically distinct class of polyps that may be difficult to detect, and little is known regarding risk factors for these lesions. Identification of risk factors for these lesions may aid in colorectal cancer (CRC) screening, because patients at risk for these lesions may require special imaging techniques. Smoking, an important risk factor for CRC, may be associated with molecular changes that increase the risk for flat adenomas. Objective The aim of this study was to examine the association between smoking and flat adenomas. Design Prospective cross-sectional study. Setting University hospital endoscopy center. Patients We enrolled asymptomatic patients presenting for CRC screening. Interventions We screened patients with a high-definition (1080i signal) wide-angle (170° field of view) Olympus 180-series colonoscope. We collected demographics, medication use, family history of CRC, diet history, and smoking history. Main Outcome Measurements Polyp morphology, assessed by using the Japanese Research Society Classification (JRSC). Results A total of 600 patients were enrolled. We observed that smoking was associated with having a flat adenoma of any size (adjusted odds ratio [OR], 2.53; 95% CI, 1.60-4.00), having only flat adenomas that were ≥6 mm in diameter (adjusted OR, 3.84; 95% CI, 2.02-7.32), as well as flat advanced adenomas (adjusted OR, 2.81; 95% CI, 1.08-7.30). Limitations The study design may not account for some confounding variables and provides no information regarding smoking status at the time of initiation of flat adenomas. Conclusion Smoking was associated with flat adenomas in our population. Our findings may explain the earlier onset of CRC in smokers as well as the advanced stage with which they present, with compared with nonsmokers. Smokers may require screening with high-definition colonoscopes to detect flat adenomas.