No effect of aspirin on mammographic density in a randomized controlled clinical trial.
BACKGROUND
Epidemiologic studies suggest a reduced risk of breast cancer among women who regularly use aspirin; a plausible mechanism is through aspirin effect on mammographic breast density, a breast cancer risk factor, possibly mediated through aspirin interference with estrogen synthesis.


METHODS
In a 2-arm randomized placebo-controlled clinical trial, we evaluated the effects of 6-month administration of 325 mg/day aspirin on total mammographic breast dense area and percent of the mammographic breast image occupied by dense areas (% density) in 143 postmenopausal women. Eligible women, recruited from 2005 to 2007, were healthy, not taking hormone therapy, with elevated mammographic breast density (American College of Radiology Breast Imaging Reporting and Data System density category 2, 3, or 4) within 6 months before enrollment.


RESULTS
Women were a mean (SD) 59.5 (5.5) years. Geometric mean baseline percent density was 17.6% (95% confidence interval, 14.8-20.9) in women randomized to aspirin and 19.2% (95% confidence interval, 16.3-22.7) in women randomized to placebo. Percent density decreased in women randomized to aspirin by an absolute 0.8% versus an absolute decrease of 1.2% in controls (P = 0.84). Total breast area and dense area decreased to a similar degree in women assigned to aspirin and in those assigned to placebo, with no statistically significant differences between trial arms.


CONCLUSIONS
A single daily administration of adult-dose aspirin for 6 months had no effect on mammographic density in postmenopausal women. If aspirin affects breast cancer risk in postmenopausal women, it may do so through alternative pathways than mammographic breast density.
Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA. amctiern@fhcrc.org
Anne
A
McTiernan
C Y
CY
Wang
Bess
B
Sorensen
Liren
L
Xiao
Diana S M
DS
Buist
Erin J
EJ
Aiello Bowles
Emily
E
White
Mary Anne
MA
Rossing
John
J
Potter
Nicole
N
Urban
D000368:Aged; D001241:Aspirin / Q000008:administration & dosage / Q000494:pharmacology*; D001943:Breast Neoplasms / Q000000981:diagnostic imaging*; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D016014:Linear Models; D008327:Mammography; D008875:Middle Aged; D017698:Postmenopause; D012307:Risk Factors
D001241:Aspirin