Effect of ultra-low-dose transdermal estradiol on breast density in postmenopausal women.
OBJECTIVE
Women with higher mammographic breast density have increased risk for breast cancer, and there is some evidence that a change in breast density may be a marker for change in risk for breast cancer. The purpose of this study was to determine whether 2 years of treatment with ultra-low-dose transdermal estradiol results in a change in breast density.


METHODS
The Ultra-Low-dose Transdermal Estradiol Assessment was a randomized, blinded, placebo-controlled trial of 2 years of treatment with unopposed ultra-low-dose (0.014 mg/d) transdermal estradiol for prevention of osteoporosis in 417 postmenopausal women with no history of breast cancer who had not had a hysterectomy. We obtained mammograms at baseline and after 1 and 2 years of treatment from 276 of the participants. Right craniocaudal views were analyzed at a central radiology facility by a trained clinician blinded to treatment group and order of acquisition. Contour analysis was performed to define dense areas versus fatty tissue. Between-group differences in mean change in percent breast density from baseline to 1 and to 2 years of follow-up were assessed using linear regression models adjusted for clinical site.


RESULTS
Participants were 66 +/- 5 years old and 94% were white. The average percent breast density at baseline was 34%. There was no significant difference between treatment groups in change in percent breast density after 1 year (between-group difference, 0.1%; 95% confidence interval, -1.3% to 1.6%) or 2 years of treatment (0.8%; -0.6% to 2.1%).


CONCLUSIONS
Two years of treatment with ultra-low-dose transdermal estradiol did not increase breast density.
Grady
Deborah
D
University of California Women's Health Clinical Research Center, San Francisco, CA 94115, USA.
Vittinghoff
Eric
E
Lin
Feng
F
Hanes
Vladimir
V
Ensrud
Kristine
K
Habel
Laurel A
LA
Wallace
Robert
R
Macer
Judith
J
Cummings
Steven R
SR
Shepherd
John
J
D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D015519:Bone Density / Q000187:drug effects; D001940:Breast / Q000187:drug effects* / Q000473:pathology*; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D004958:Estradiol / Q000008:administration & dosage* / Q000009:adverse effects; D015914:Estrogen Replacement Therapy / Q000379:methods*; D005260:Female; D006801:Humans; D008327:Mammography; D008875:Middle Aged; D015663:Osteoporosis, Postmenopausal / Q000188:drug therapy; D017698:Postmenopause; D012107:Research Design; D016896:Treatment Outcome; D016387:Women's Health
D004958:Estradiol