Effects of different types of hormone replacement therapy on mammographic density

Objectives: to evaluate the effects of different types of hormone replaceme nt therapy (HRT) on mammographic density in postmenopausal women. Methods: In a prospective 1-year study, 121 healthy postmenopausal women were alloca ted to one of the following five study groups: twenty-six women were treate d with continuous transdermal 17beta-estradiol 50 mcg/die plus acetate nome gestrolo 5 mg/die sequentially added for 12 days per month (Group A), 25 wo men were treated with continuous transdermal 17beta-estradiol 50 mcg/die pl us acetate nomegestrolo 2.5 mg/die added every day (Group B), 23 women were treated with continuous transdermal 17beta-estradiol 50 mcg/die (Group C) 24 women were treated with tibolone 2.5 mg/die (Group D): and 23 women not receiving any medication represented the control group (Group E). At the ti me of recruitment and after 12 months a two-view mammography was performed to evaluate mammographic density according to a quantitative method: type I (less than 25% of mammary gland covered by dense tissue), type 2 (from 25 to 75% of total glandular area covered by dense tissue), type 3 (more than 75% or mammary parenchyma covered by dense tissue). Results: After 12 month s of HRT, seven out of 20 patients (35%) in group A. nine of 21 patients (4 2.85%) in group B, four out of 19 patients in group C and two of 20 patient s (10%) in group D, showed an increase in mammographic density. No variatio n of density was observed at the second mammographic test in the control gr oup. The mammographic density increase which occurred in groups A., B and C was statistically significant (P < 0.05) when compared with group E: no st atistically significant difference (P = 0.49) was found in mammographic den sity increase between group D and group E. When the different treatment typ es were compared each other, a statistically significant difference (P = 0. 04) was found only between the mammographic density increase occurring in g roups B and D. Conclusions: HRT may cause an increase of mammographic densi ty. The frequency of the density increase is related to the type of HRT and a replacement therapy including a progestin, especially in continuous comb ination with estrogen. leads to more evident mammographic changes, Tibolone does not significantly affect mammographic density. (C) 2001 Elsevier Scie nce Ireland Ltd. All rights reserved.