Low-dose aspirin and risk of gastric and oesophageal cancer: A population-based study in the United Kingdom using The Health Improvement Network.

There is increasing interest regarding potential protective effects of low-dose aspirin against various gastrointestinal cancers. We aimed to quantify the association between use of low-dose aspirin and risk of gastric/oesophageal cancer using a population-based primary care database in the UK. Between January 2005 and December 2015, we identified a cohort of 223 640 new users of low-dose aspirin (75-300 mg/day) and a matched cohort of nonusers at the start of follow-up from The Health Improvement Network. Cohorts were followed to identify incident cases of gastric/oesophageal cancer. Nested case-control analyses were conducted and adjusted odds ratios (ORs) with 95% confidence intervals (CIs) were calculated for current vs nonuse of low-dose aspirin using logistic regression. Current use was defined as when low-dose aspirin lasted 0 to 90 days before the index date (event date for cases, random date for controls) and previous duration was ≥1 year. We identified 727 incident cases of gastric cancer and 1394 incident cases of oesophageal cancer. ORs (95% CIs) were 0.46 (0.38-0.57) for gastric cancer and 0.59 (0.51-0.69) for oesophageal cancer. The effect remained consistent with no clear change seen between previous duration of low-dose aspirin use of 1-3, 3-5 or >5 years. The reduced risks was seen with 75 mg/day, and effects were consistent in lag-time analyses. In conclusion, our results indicate that use of low-dose aspirin is associated with a 54% reduced risk of gastric cancer and a 41% reduced risk of oesophageal cancer as supported by mechanistic data.