title: A cohort study investigating aspirin use and survival in men with prostate cancer.
abstract: BACKGROUND
  Aspirin use has been associated with reduced mortality from cancer including prostate cancer in some studies. A number of anti-cancer mechanisms of aspirin have been proposed, including the inhibition of the cyclooxygenase enzymes, through which aspirin mediates both anti-platelet and anti-inflammatory activities. This cohort study examines associations between pre-diagnostic aspirin use (overall and by dose and dosing intensity) and mortality in men with localised prostate cancer.
  
  
  METHODS
  Men with stage I-III prostate cancer were identified from Irish National Cancer Registry records, which have been linked to national prescribing data from the Irish General Medical Services scheme. Aspirin use in the year preceding prostate cancer diagnosis was identified from this linked prescription-claims data. Adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated for associations between aspirin use and all-cause and prostate cancer-specific mortality. Associations between prescribed dose and dosing intensity were examined. The presence of effect modification by the type of treatment received and tumour characteristics was also assessed.
  
  
  RESULTS
  Two thousand nine hundred and thirty-six men with a diagnosis of stage I-III prostate cancer (2001-2006) were identified (aspirin users, n = 1131). The median duration of patient follow-up was 5.5 years. In adjusted analyses, aspirin use was associated with a small, but non-significant, reduced risk of prostate cancer-specific mortality (HR = 0.88, 95% CI 0.67-1.15). In dose-response analyses, stronger associations with prostate cancer-specific mortality were observed in men with higher aspirin dosing intensity (HR = 0.73, 95% CI 0.51-1.05) and in men receiving >75 mg of aspirin (HR = 0.61, 95% CI 0.37-0.99). Analyses of effect modification by treatment type or tumour characteristics were non-significant.
  
  
  CONCLUSIONS
  Consistent with prior studies, aspirin use was associated with a non-significant reduced risk of prostate cancer-specific mortality in men with localised prostate cancer. Men receiving higher doses of aspirin had a statistically significant reduced risk of prostate cancer-specific mortality. These findings regarding an aspirin dose require further investigation.
authors.affiliation: Department of Pharmacology and Therapeutics, Trinity College, University of Dublin, Dublin, Ireland.
authors.forename: E M
authors.initials: EM
authors.lastname: Flahavan
authors.forename: K
authors.initials: K
authors.lastname: Bennett
authors.forename: L
authors.initials: L
authors.lastname: Sharp
authors.forename: T I
authors.initials: TI
authors.lastname: Barron
mesh_terms: D000368:Aged; D001241:Aspirin / Q000494:pharmacology / Q000627:therapeutic use*; D015331:Cohort Studies; D003131:Combined Modality Therapy; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology / Q000627:therapeutic use*; D006801:Humans; D008297:Male; D008875:Middle Aged; D016016:Proportional Hazards Models; D011471:Prostatic Neoplasms / Q000401:mortality* / Q000628:therapy; D012306:Risk; D016896:Treatment Outcome
chemical_list: D016861:Cyclooxygenase Inhibitors; D001241:Aspirin
keywords: aspirin; mortality; pharmacoepidemiology; prostate neoplasm