The effects of exogenous estrogen replacement therapy of the breast: Breast cancer risk and mammographic parenchymal patterns

Abstract

A retrospective pilot study was implemented to better define the potential carcinogenic role of conjugated equine estrogen (Premarin®) on the breast, and the influence of these hormone analogues on proliferative and atrophic breast parenchyma as determined by high‐quality serial xeromammograms. Four hundred and five postmenopausal (spontaneous and surgical) women (mean age 59.7 years) were group matched for the risk factors of age and parity. The dominant parenchymal pattern (N1P1P2DY) as disclosed mammographically was determined for each patient, who was then categorized into one of four groups: Group 1 Asymptomatic—no hormones, 124 patients; Group 2 Symptomatic—no hormones, 75 patients; Group 3 Asymptomatic—hormones, 152 patients; and Group 4 Symptomatic—hormones, 54 patients. Patients in Groups 3 and 4 were treated with therapeutic estrogens a minimum of 18 months (mean 79 months) and follow‐up ranged from 39–344 months. In the entire series, 25 carcinomas (6.2%) were detected. In Group 3, five carcinomas (2.4%) were detected, but two cancers (1.0%) were found in symptomatic estrogen users. The occurrence of carcinoma in Group 2 was greater than the remaining categories; however, cancer risk was not statistically greater in any category with regard to hormone replacement therapy. Patients treated with therapeutic estrogens were observed to have an increase of 8.9% in the frequency of a more glandular (P2, DY) mammographic parenchymal pattern and this was noted to be within the range of interpretation error of the mammographer. This suggests a physiologic effect of therapeutic estrogens on atrophic breast parenchyma with conversion to a glandular, proliferative state. This study suggests that long‐term replacement estrogen therapy for postmenopausal symptoms does not significantly alter mammographic parenchymal patterns and that the use of these compounds in therapeutic doses does not increase the risk of breast cancer. Copyright © 1980 American Cancer Society