Nonsteroidal anti-inflammatory drugs but not aspirin are associated with a lower risk of post-colonoscopy colorectal cancer.

BACKGROUND:Although nonsteroidal anti-inflammatory drugs (NSAIDs) reduce colorectal cancer (CRC) risk, their role in preventing post-colonoscopy CRC (PCCRC) remains undetermined. AIMS:To investigate whether NSAIDs reduce PCCRC risk after a negative baseline colonoscopy METHODS: This is a retrospective cohort study based on a territory-wide healthcare database of Hong Kong. All patients (aged 40 or above) who underwent colonoscopies between 2005 and 2013 were identified. Exclusion criteria included CRC detected within 6 months of index colonoscopy, prior CRC, inflammatory bowel disease and prior colectomy. The primary outcome was PCCRC-3y diagnosed between 6 and 36 months after index colonoscopy. Sites of CRC were categorised as proximal (proximal to splenic flexure) and distal. The adjusted hazards ratio (aHR) of PCCRC-3y with NSAID and aspirin use (defined as cumulative use for ≥90 days within 5 years before index colonoscopy) was derived by propensity score (PS) regression adjustment of 22 covariates (including patient factors, concurrent medication use and endoscopy centre's performance). RESULTS:Of 187 897 eligible patients, 21 757 (11.6%) were NSAID users. 854 (0.45%) developed PCCRC-3y (proximal cancer: 147 [17.2%]). NSAIDs were associated with a lower PCCRC-3y risk (aHR: 0.54, 95% CI: 0.41-0.70), but not CRC that developed >3 years (aHR: 0.78, 95% CI 0.56-1.09). The aHR was 0.48 (95% CI: 0.24-0.95) for proximal and 0.55 (95% CI: 0.40-0.74) for distal cancer. A duration- and frequency response relationship was observed (Ptrend  < 0.001). For aspirin, the aHR was 1.01 (95% CI: 0.80-1.28). CONCLUSIONS:Non-aspirin NSAIDs were associated with lower PCCRC risk after a negative baseline colonoscopy.