Date of Award


Degree Type

Selective Evidence-Based Medicine Review

Degree Name

Master of Science in Health Sciences - Physician Assistant


Physician Assistant Studies

Department Chair

John Cavanagh, PhD, PA-C


OBJECTIVE: The objective of this selective EBM review is to determine whether or not aspirin is effective in helping to prevent breast cancer in women ages 45 years and older.

STUDY DESIGN: Review of three English language primary studies published in 2005, 2007, and 2008

DATA SOURCES: Two randomized, double blind, placebo controlled clinical trials and one prospective, population based cohort study comparing aspirin to placebo were found using PubMed and Cochrane databases.

OUTCOMES MEASURED: Breast cancer development was measured in several ways. Tumor characteristics were measured at diagnosis, including size, metastasis to lymph nodes, histology of the mass, histology differentiation, and estrogen and progesterone status. Outcomes were also measured by pathology reports, cytology reports, on strong clinical and radiologic or laboratory marker evidence, and also self reported questionnaire.

RESULTS: The two randomized controlled trials showed that the use of aspirin has no significant effect on the prevention of breast cancer. The cohort study showed an inverse relationship between the use of aspirin and the risk of cancer incidence and mortality.

CONCLUSIONS: Although the two RCTs showed no effect of aspirin on the prevention of breast cancer, the cohort study showed some promise in the use of aspirin and breast cancer prevention. The dose of aspirin used in the RCTs was only 100mg, and the doses in the cohort study varied based on individual reporting. Increasing the dose of aspirin to 325mg in future studies may show some effect in the prevention of breast cancer.