681PDLow-dose aspirin and risk of gastric and oesophageal cancer: A population-based study

Abstract Background Evidence suggests that low-dose aspirin is associated with a 30–40% protective effect against colorectal cancer (CRC) yet its effect on other gastrointestinal cancers has been less studied. 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 United Kingdom – The Health Improvement Network. Methods Among persons aged 40–89 years from 2005–2015, ∼200,000 new users of low-dose aspirin (75–300 mg/day) were each matched to a non-user by age, sex, time since study entry and number of primary care visits in the previous year. Individuals were followed (max. 18 years) to identify incident cases of gastric/oesophageal cancer. Nested case–control analyses were conducted using 5000 controls for both sets of cancer cases frequency matched by age, sex and calendar year. Adjusted odds ratios (ORs) with 95% confidence intervals (CIs) were calculated for current vs. non-use of low-dose aspirin using logistic regression. Current use was when low-dose aspirin use lasted to 0–90 days before the index date (event date for cases, random date for controls) and total duration of use before the index date was >1 year; non-use was no use of low-dose aspirin ever before the index date or use that ended ≥1 year before the index date. Results We identified 727 incident cases of gastric cancer and 1394 incident cases of oesophageal cancer. As shown in the table, compared with non-use, current use of low-dose aspirin was associated with a significant 54% reduced risk of gastric cancer and a significant 41% reduced risk of oesophageal cancer. Protective effects were seen for both cancers irrespective of total previous duration of low-dose aspirin use. Table:681PD Odds ratios (95% confidence intervals) for the association between use of low-dose aspirin (current vs non-use) and gastric/oesophageal cancerGastric cancerOesophageal cancerCases N = 727 n (%)Controls N = 5000 n (%)Adjusted OR* (95% CI)Cases N = 1394 n (%)Controls N = 5000 n (%)Adjusted OR* (95% CI)Non-use of low-dose aspirin442 (60.8)2404 (48.1)1.0 (reference)829 (59.5)2555 (51.1)1.0 (reference)Current use of low-dose aspirin (with duration >1 year)146 (20.1)1407 (28.1)0.46 (0.38-0.57)331 (23.7)1397 (27.9)0.59 (0.51-0.69)Duration >1 to =3 years90 (12.4)714 (14.3)0.60 (0.47-0.77)186 (13.3)717 (14.3)0.68 (0.56-