Effect of long-term continuous combined hormone replacement therapy with estradiol valerate and either dienogest or norethisterone acetate on mammographic density in postmenopausal women.

INTRODUCTION: The potential effect of hormone replacement therapy (HRT) on the appearance of the breast on screening mammography is of considerable interest and may have important practical implications. OBJECTIVE: The aim of this study was to evaluate the changes in the mammographic breast density during long-term continuous combined HRT with 2 different preparations. MATERIAL AND METHODS: Nineteen patients were studied. Fifteen were treated with Climodien (Schering, 2 mg estradiol and 2 mg dienogest [E2/dienogest]), and 4 patients were treated with Kliogest (Novo Nordisk, 2 mg estradiol and 1 mg norethisterone acetate [E2/NETA]). All were followed with yearly mammography for 4 years. RESULTS: Increase in the mammographic density was noted in 3 patients (15.8%). The change was evident after the first year of treatment with no further change during the rest of the study period. CONCLUSIONS: Long-term therapy with continuous combined HRT (E2/dienogest or E2/NETA) increased breast density in 3/19 (15.8%) of the patients. Our results suggest that the effect of these HRT preparations on mammographic density may be less significant than suggested by the results of similarly designed trials evaluating different HRT preparations.