Background: Oestrogens usually stimulate the progression of oestrogen receptor (ER)-
positive breast cancer. Paradoxically, high-dose oestrogens suppress the growth of these
tumours in certain circumstances. Methods: We prospectively examined the efficacy and
safety of ethinylestradiol treatment (3 mg per day oral) in postmenopausal patients with
advanced or recurrent ER-positive breast cancer who had previously received endocrine
therapies, especially those with resistance to aromatase inhibitors. Results: Eighteen …

Iwase H, Yamamoto Y, Yamamoto-Ibusuki M, et al (Kumamoto Univ, Chuo-ku, Japan; et al)
Br J Cancer 109:1537-1542, 2013§ … Ethinylestradiol is beneficial for postmenopausal
patients with heavily pre-treated metastatic breast cancer after prior aromatase inhibitor
treatment: a prospective study Iwase H, Yamamoto Y, Yamamoto-Ibusuki M, et al (Kumamoto
Univ, Chuo-ku, Japan; et al) Br J Cancer 109:1537-1542, 2013§ …