Effect of smoking on the risk of gastrointestinal cancer after cholecystectomy: A national population-based cohort study

BACKGROUND The role of smoking in the incidence of colorectal cancer (CRC) or gastric cancer (GC) in populations undergoing cholecystectomy has not been investigated. AIM To evaluate the effect of smoking on CRC or GC development in cholecystectomy patients. METHODS A total of 174874 patients who underwent cholecystectomy between January 1, 2010 and December 31, 2017 were identified using the Korean National Health Insurance Service claims database. These patients were matched 1:1 with members of a healthy population according to age and sex. CRC or GC risk after cholecystectomy and the association between smoking and CRC or GC risk in cholecystectomy patients were evaluated using adjusted hazard ratios (HRs) and 95%CIs. RESULTS The risks of CRC (adjusted HR: 1.15; 95%CI: 1.06-1.25; P = 0.0013) and GC (adjusted HR: 1.11; 95%CI: 1.01-1.22; P = 0.0027) were significantly higher in cholecystectomy patients. In the population who underwent cholecystectomy, both CRC and GC risk were higher in those who had smoked compared to those who had never smoked. For both cancers, the risk tended to increase in the order of non-smokers, ex-smokers, and current smokers. In addition, a positive correlation was observed between the amount of smoking and the risks of both CRC and GC. CONCLUSION Careful follow-up and screening should be performed, focusing on the increased risk of gastrointestinal cancer in the cholecystectomy group, particularly considering the individual smoking habits.