Prophylactic aspirin intake and breast cancer risk; A systematic review and meta-analysis of observational cohort studies.

ABSTRACT

Breast Cancer (BC) is the most common cancer amongst women. The chemo-preventative effects of aspirin on breast cancer have been demonstrated in several longitudinal studies however previous meta-analysis have shown inconsistent results. This study aimed to assess the relationship between aspirin use and BC risk, and to determine if there is a dose-response relationship between aspirin and BC risk. Studies incorporating BC risk with aspirin use published within the last twenty years were included. The study report is based on the guidelines of Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) and Meta-Analysis of Observational Studies in Epidemiology. Twenty-eight cohort studies that reported BC incidence during a follow up of 4.4-32 years were included. Compared to non-users, aspirin users had a reduced risk of BC (HR = 0.91, c.i 0.81-0.97, p = 0.002). There was no obvious association between BC risk reduction and aspirin dose (HR = 0.94, c.i 0.85-1.04) or duration (HR = 0.86, c.i 0.71-1.03). Frequency, however, was associated with a reduced risk of BC (HR = 0.90, c.i 0.82-0.98). A risk reduction was observed in oestrogen receptor (ER) positive tumours (HR = 0.90, c.i 0.86-0.96, p = 0.0004) while no relationship was observed with ER negative tumours (HR = 0.94, c.i 0.85-1.05). This meta-analysis found an association between aspirin intake and BC risk reduction. A more favourable outcome was noted with ingestion of greater than 6 tablets of aspirin per week. Aspirin had a significant risk reduction in patients with ER positive tumours compared to ER negative BC.