• Cancer Prevention Fellowship Program, Division of Cancer Prevention, National Cancer Institute, Rockville, Maryland.
• Early Detection Research Branch, Division of Cancer Prevention, National Cancer Institute, Rockville, Maryland.
• Gastrointestinal and Other Cancers Research Group, Division of Cancer Prevention, National Cancer Institute, Rockville, Maryland.

IMPORTANCE: Many studies have evaluated the long-term benefits of aspirin use; however, the association of aspirin use with cancer incidence and survival in older individuals remains uncertain. Additional population-based evidence of this association is necessary to better understand any possible protective effects of aspirin in older adults.

OBJECTIVE: To investigate the association of aspirin use with risk of developing new cancers and site-specific cancer-associated survival in bladder, breast, esophageal, gastric, pancreatic, and uterine cancers.

DESIGN, SETTING, AND PARTICIPANTS: This cohort study used data from the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial. Participants were aged 65 years or older at baseline (1993-2001) or reached age 65 during follow-up. Data analysis was conducted from January to June 2020.

MAIN OUTCOMES AND MEASURES: Incidence of and survival from the investigated cancer types. Univariable and multivariable hazard ratios (HRs) and 95% CIs were calculated using Cox proportional hazards regression modeling, adjusting for covariates. Multivariable models for incidence included time-varying covariates.

RESULTS: A total of 139 896 individuals (mean [SD] age at baseline, 66.4 [2.4] years; 71 884 [51.4%] women; 123 824 [88.5%] non-Hispanic White individuals) were included in the analysis. During the study period, 32 580 incident cancers (1751 [5.4%] bladder, 4552 [14.0%] breast, 332 [1.0%] esophageal, 397 [1.2%] gastric, 878 [2.7%] pancreatic, and 716 [2.2%] uterine cancers) were reported. Aspirin use was not associated with incidence of any of the investigated cancer types among individuals aged 65 years or older. Multivariable regression analysis demonstrated that aspirin use at least 3 times/week was associated with increased survival among patients with bladder (HR, 0.67; 95% CI, 0.51-0.88) and breast (HR, 0.75; 95% CI, 0.59-0.96) cancers but not among those with esophageal, gastric, pancreatic, or uterine cancer. A similar association of any aspirin use with bladder (HR, 0.75; 95% CI, 0.58-0.98) and breast (HR, 0.79; 95% CI, 0.63-0.99) cancer survival was observed.

CONCLUSIONS AND RELEVANCE: In the current study, any aspirin use and aspirin use at least 3 times/week was associated with improved bladder and breast cancer survival. Associations between aspirin use and incidence of any of the investigated cancers or between aspirin use and esophageal, gastric, pancreatic, or uterine cancer survival were not observed.