Successful ethinylestradiol therapy for a metastatic breast cancer patient with heavily pre-treated with endocrine therapies

The critical strategy leading to the success of endocrine therapy in metastatic breast cancer is ex tended duration of treatment. Here, we report a case with late-stage metastatic breast cancer who dramatically responded to high-dose estrogen treatment with a long-term stable disease. A 52-year-old female with metastatic breast cancer was referred to our hospital. She had already received several courses of systemic therapy: LH-RH agonist and tamoxifen and docetaxel. At first visit to us, she had a multiple liver tumor and an irregular mass in the left breast. We started endocrine therapy of LH-RH agonist and anastrozole with a stable disease for 12 months. After the disease progression, LH-RH agonist and letrozole, TS-1, vinorelubine, and nab-paclitaxel were administered. Further, she received the exemestane therapy as the fifth line, but the disease progressed after 4 months. We then started ethinylestradiol (EE2) therapy. Two months later, the tumor in liver rapidly decreased from 15.8 to 10.6 cm, of which the tumor shrinkage rate was 33 %. Subsequently, the patient had stable disease for 12 months. After 14-month EE2 therapy, the patient had a regrowth of the liver tumors, and was then treated with letrozole again. This therapy had continued for 5 months. Estrogen therapy is beneficial for postmenopausal patients with heavily pre-treated who could have acquired resistance to aromatase inhibitor.