Differential impact of conventional and low-dose oral hormone therapy, tibolone and raloxifene on mammographic breast density, assessed by an automated quantitative method.

OBJECTIVE

To evaluate impact of different postmenopausal hormone therapy (HT) regimens and raloxifene on mammographic breast density.

DESIGN

Open, randomised, comparative clinical trial.

SETTING

Women were recruited through local newspapers and posters. They were examined at the Departments of Haematology, Gynaecology, and Radiology in a University Hospital.

POPULATION

A total of 202 healthy postmenopausal women between the age of 45 and 65 years.

METHODS

Women were randomly assigned to receive daily treatment for 12 weeks with tablets containing low-dose HT containing 1 mg 17 beta-estradiol + 0.5 mg norethisterone acetate (NETA) (n = 50), conventional-dose HT containing 2 mg 17 beta-estradiol and 1 mg NETA (n = 50), 2.5 mg tibolone (n = 51), or 60 mg raloxifene (n = 51). Mammographic density was determined at baseline and after 12 weeks by an automated technique in full-field digital mammograms.

MAIN OUTCOME MEASURES

Mammographic density was expressed as volumetric breast density estimations.

RESULTS

Mammographic breast density increased significantly and to a similar degree in both the conventional- and low-dose HT groups. A small reduction in mammographic breast density was seen in the raloxifene group, whereas those allocated to tibolone treatment only showed minor changes.

CONCLUSIONS

Our findings demonstrated a significant difference in impact on mammographic breast density between the regimens. Although these results indicate a differential effect of these regimens on breast tissue, the relation to breast cancer risk remains unresolved.