Aspirin exposure and its association with metal stent patency in malignant distal biliary obstruction: a large international multicenter propensity score-matched study.

BACKGROUND AND AIMS:Stent dysfunction is common after ERCP with self-expandable metal stent (SEMS) insertion for malignant distal biliary obstruction (MDBO). Chronic aspirin (acetylsalicylic acid; ASA) exposure has been previously shown to potentially decrease this risk. We aim to further ascertain the protective effect of ASA and to identify other predictors of stent dysfunction. METHODS:This multicenter retrospective cohort study was conducted at 9 sites in Canada and 1 in the United States. Patients with MDBO who underwent ERCP with SEMS placement between January 2014 and December 2019 were included and divided into 2 cohorts: ASA exposed (ASA-E) and ASA unexposed (ASA-U). Propensity-score matching (PSM) was performed to limit selection bias. Matched variables were age, sex, tumor stage, and type of metal stent. The primary outcome was the hazard rate of stent dysfunction. A multivariable Cox proportional hazards model was used to identify independent predictors of stent dysfunction. RESULTS:Of 1396 patients assessed, after PSM 496 patients were analyzed (248 ASA-E and 248 ASA-U). ERCP with SEMS placement was associated with a high clinical success of 82.2% in ASA-E and 81.2% in ASA-U cohorts (P = .80). One hundred eighty-four patients had stent dysfunction with a mean stent patency time of 229.9 ± 306.2 days and 245.4 ± 241.4 days in ASA-E and ASA-U groups, respectively (P = .52). On multivariable analysis, ASA exposure did not protect against stent dysfunction (hazard ratio [HR], 1.25; 95% confidence interval [CI], .96-1.63). An etiology of pancreatic cancer (HR, 1.36; 95% CI, 1.15-1.61) predicted stent dysfunction, whereas cancer therapy was protective (HR, .73; 95% CI, .55-.96). Chronic ASA use was not associated with an increased risk for adverse events including bleeding, post-ERCP pancreatitis, and perforation. CONCLUSIONS:In this large, multicenter study using PSM, chronic exposure to ASA did not protect against stent dysfunction in MDBO. Instead, the analysis revealed that the etiology of pancreatic cancer was an independent predictor of stent dysfunction and cancer therapy was protective.