Aromatase inhibitors affect vaginal proliferation and steroid hormone receptors.

Objective: Women with breast cancer who are treated with aromatase inhibitors often experience vaginal atrophy symptoms and sexual dysfunction. This work aims to study proliferation and the presence and distribution of steroid hormone receptors in vaginal biopsies in relation to vaginal atrophy and vaginal pH in women with breast cancer who are on adjuvant endocrine treatment and in healthy postmenopausal women.
Methods: This is a cross-sectional study that compares postmenopausal aromatase inhibitor-treated women with breast cancer (n = 15) with tamoxifen-treated women with breast cancer (n = 16) and age-matched postmenopausal women without treatment (n = 19) or with vaginal estrogen therapy (n = 16). Immunohistochemistry was used to study proliferation and steroid hormone receptor staining intensity. Data was correlated with estrogen and androgen levels, vaginal atrophy scores, and vaginal pH.
Results: Aromatase inhibitor-treated women had a lower grade of proliferation, weaker progesterone receptor staining, and stronger androgen receptor staining, which correlated with plasma estrone levels, vaginal atrophy scores, and vaginal pH.
Conclusions: Women with aromatase inhibitor-treated breast cancer exhibit reduced proliferation and altered steroid hormone receptor staining intensity in the vagina, which are related to clinical signs of vaginal atrophy. Although these effects are most probably attributable to estrogen suppression, a possible local inhibition of aromatase cannot be ruled out.