Hormone replacement therapy and breast density changes.

OBJECTIVES: To compare the incidence of increased breast density and tenderness in postmenopausal women associated with transdermal (Estalis/Combipatch), Novartis, Basel, Switzerland) and oral (Kliogest), Schering AG, Berlin, Germany) hormone replacement therapy (HRT). METHODS: A total of 202 postmenopausal women were randomized to transdermal or oral HRT. Mammograms obtained at study entry and after 1 year of treatment were assessed for percent breast density by means of the digital segmentation and thresholding technique. Breast tenderness was assessed at each study visit. RESULTS: The mean breast density by ANCOVA after adjusting for screening value at study end was significantly lower for women using Estalis (38.4%, standard error 0.9%) compared with Kliogest (46.9%, standard error 1.5%) (p<0.0001). Significantly fewer women using transdermal HRT had an increase in mammographic breast density or breast tenderness compared to oral HRT. Of the women using transdermal HRT, 39.1% had no change in breast density compared to 15.7% for women using oral HRT. Only 4% of women using transdermal HRT had a marked increase in density (>25%) compared to 15.7% of women using oral HRT. Overall, 36.0% of patients in the transdermal group reported breast tenderness at some point during the 1-year study, compared with 57.6% in the oral HRT group (p=0.0002). CONCLUSION: Transdermal HRT use is associated with a significantly lower incidence of increased mammographic breast density and breast tenderness compared with oral HRT.