Mammographic breast density during hormone replacement therapy: effects of continuous combination, unopposed transdermal and low-potency estrogen regimens.
OBJECTIVE
The aim of this study was to evaluate the impact of different hormone replacement therapy (HRT) regimens on mammographic breast density.


METHODS
Mammographic density was recorded in women participating in a population-based screening program. At first mammogram, all women were non-users of HRT, and thereafter reported continuous use of the same HRT regimen. The study population comprised 158 women: a total of 52 women were using continuous combined HRT (conjugated equine estrogen 0.625 mg plus medroxyprogesterone acetate 5 mg); 51 women were using low-dose oral estrogen alone (estriol 2 mg daily); and 55 women were using unopposed transdermal estrogen given as a patch (estradiol 50 micrograms/24 h). Films were coded and analyzed for mammographic density by an independent radiologist blinded to treatments. Mammographic density was classified according to Wolfe.


RESULTS
An increase in mammographic density was much more common among women taking continuous combined HRT (40%) than for those using oral low-dose estrogen (6%) and transdermal (2%) treatment. The increase in density was already apparent at the first visit after starting HRT. During long-term follow-up, there was very little change in mammographic status.


CONCLUSIONS
HRT regimens were shown to have different effects on the normal breast. There is an urgent need to clarify the biological nature and significance of a change in mammographic density during treatment and, in particular, its relation to symptoms and breast cancer risk.
Lundström
E
E
Department of Obstetrics and Gynecology, Karolinska Hospital, Stockholm, Sweden.
Wilczek
B
B
von Palffy
Z
Z
Söderqvist
G
G
von Schoultz
B
B
D000279:Administration, Cutaneous; D000284:Administration, Oral; D000328:Adult; D000704:Analysis of Variance; D004359:Drug Therapy, Combination; D004964:Estriol / Q000008:administration & dosage* / Q000009:adverse effects*; D015914:Estrogen Replacement Therapy / Q000009:adverse effects* / Q000379:methods*; D004966:Estrogens, Conjugated (USP) / Q000008:administration & dosage* / Q000009:adverse effects*; D005260:Female; D005348:Fibrocystic Breast Disease / Q000139:chemically induced* / Q000145:classification / Q000000981:diagnostic imaging*; D005500:Follow-Up Studies; D006801:Humans; D008327:Mammography; D017258:Medroxyprogesterone Acetate / Q000008:administration & dosage* / Q000009:adverse effects*; D008875:Middle Aged; D045167:Progesterone Congeners / Q000008:administration & dosage* / Q000009:adverse effects*; D016037:Single-Blind Method
D004966:Estrogens, Conjugated (USP); D045167:Progesterone Congeners; D017258:Medroxyprogesterone Acetate; D004964:Estriol