Aspirin is associated with lower risk of pancreatic cancer and cancer-related mortality in patients with diabetes mellitus

Background Patients with type 2 diabetes mellitus (T2DM) have higher pancreatic cancer (PC) risk. While aspirin has chemopreventive effects on digestive cancers, its effect on PC among patients with T2DM is unclear. Methods This retrospective cohort study identified newly diagnosed adult patients with T2DM in Hong Kong between 2001 and 2015 from a territory-wide healthcare registry. Exclusion criteria were history of PC, pancreatic cyst, IgG4 disease, or pancreatectomy. To address reverse causality between PC and T2DM, we excluded patients with PC diagnosed within 1 year of T2DM. We also excluded patients with less than 1 year of observation. Primary outcome was PC, and secondary outcomes were PC-related and all-cause mortality. Aspirin use was treated as time-varying variable (>= 180 day-use/year) to address immortal-time bias, and multivariable Cox regression model was employed to derive adjusted HR (aHR). Propensity-score (PS) matching was used as secondary analysis. Results Among 343 966 newly diagnosed patients with T2DM (median follow-up: 10.5 years; IQR: 7.7-14.5 years), 1224 (0.36%) developed PC. There were 51 151 (14.9%) deaths from any cause, and 787 (0.2%) died from PC. Aspirin use was associated with lower PC risk in both time-dependent (aHR: 0.58; 95% CI 0.49 to 0.69) and PS matching analysis (aHR: 0.61; 95% CI 0.48 to 0.77). An inverse relationship was observed with increasing dose and duration of aspirin use (Ptrend<0.001). Aspirin was also associated with a lower risk of PC-related mortality (aHR: 0.43; 95% CI 0.34 to 0.53) and all-cause mortality (aHR: 0.78; 95% CI 0.76 to 0.80). Conclusion Aspirin use may be an oncopreventive strategy to reduce PC risk in patients with T2DM. Further studies are warranted to validate the study findings.