Mammographic breast density changes after 1 year of tibolone use

Hormone replacement therapy (HRT) is widely used with a large variety of regimens and medications. For each of these regimens the goal is the same but there is always a fear about side effects, especially on breast. Mammographic screening is a standard tool for all women receiving hormone replacement therapy. Breast density is very important, because it interferes with the sensitivity of the evaluation and it is also a predictor of malignity.

We planned a study to investigate the effects of tibolone on mammographic breast density.

We studied 70 postmenopausal women who started tibolone therapy (2.5 mg per day) after initial mammography and blood samples taken for biochemical examinations. None of the women used any hormone replacement therapy before. Eleven of them either discontinued the therapy or lost contact. After 1 year, we evaluated 59 women by mammographic status, using Wolfe classification. Mammographies were analyzed by two independent radiologists.

Mammographies of 59 women were compared with the initial ones. While in the low density patterns, there was a slight increase (15%; P < 0.05); in the higher density groups, there was a decrease of 25% as observed by one radiologist, and 16% according to the other (P < 0.05). None of the women had a diffuse, high density pattern. There was no statistically significant inter-observer variation between two radiologists (P < 0.05).

Wolfe classification allows easy interpretation of mammographic evaluation and the results are reproducible. Tibolone, as a tissue-specific steroid, does not have an estrogenic effect on breast cells. We found that it might limit, even reverse breast density increase, especially in postmenopausal women with high breast density.