Aspirin and serum estrogens in postmenopausal women: a randomized controlled
clinical trial.
Author(s): Duggan C(1), Wang CY(1), Xiao L(1), McTiernan A(2).
Affiliation(s): Author information:
(1)Division of Public Health Sciences, Fred Hutchinson Cancer Research Center,
Seattle, Washington. (2)Division of Public Health Sciences, Fred Hutchinson
Cancer Research Center, Seattle, Washington. Department of Epidemiology, School
of Public Health and Community Medicine, University of Washington, Seattle,
Washington. amctiern@fhcrc.org.
Publication date & source: 2014, Cancer Prev Res (Phila). , 7(9):906-12
Epidemiologic studies suggest a reduced risk of breast cancer among women who use
aspirin. A plausible mechanism is through aspirin's effect on estrogens, possibly
mediated through interference with estrogen synthesis via reduction in
inflammation, which is increased in adipose tissues, including breast. In a
randomized placebo-controlled trial, we evaluated the effects of six-month
administration of 325 mg/day aspirin on serum estrogens (estradiol, estrone, free
estradiol, and bioavailable estradiol) and sex hormone-binding globulin (SHBG) in
144 healthy postmenopausal women. Eligible participants, recruited 2005-2007,
were not taking nonsteroidal anti-inflammatory medication, including aspirin >2
times/week or menopausal hormone therapy, and had a Breast Imaging-Reporting and
Data System (BI-RADS) mammographic density classification of 2, 3, or 4. The
intervention effects (intent-to-treat) were evaluated by differences in the
geometric mean outcome changes at six months between aspirin and placebo groups
using generalized estimating equations (GEE). Participants were a mean 59.4 (SD,
5.4) years of age, with a mean body mass index (BMI) of 26.4 (SD, 5.4) kg/m(2).
Between baseline and six months, none of the serum estrogens or SHBG changed
substantially and there were no differences between groups. Stratifying by BMI
did not change results. In conclusion, a single daily administration of 325 mg of
aspirin for six months had no effect on serum estrogens or SHBG in postmenopausal
women. Larger doses or longer duration of aspirin administration may be needed to
affect circulating estrogens. Alternately, if aspirin influences breast cancer
risk in postmenopausal women, it may do so through direct breast tissue effects,
or through pathways other than estrogens.
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