er(+), her2(-), postmenopausal adult (ages 18-65 years, inclusive) chinese women with proven diagnosis of adenocarcinoma of the breast with evidence locoregionally recurrent or metastatic disease not amenable to resection or radiation therapy with curative intent and for whom chemotherapy is not clinically indicated.

postmenopausal women: i. prior bilateral surgical oophorectomy; or ii. medically confirmed post-menopausal status defined as spontaneous cessation of regular menses for at least 12 consecutive months with no alternative pathological or physiological cause b. documentation of histologically or cytologically confirmed diagnosis of: i. er(+) breast cancer. c. documentation of her2(-) breast cancer. d. previously untreated with any systemic anti cancer therapy for their locoregionally recurrent or metastatic er+ disease.

measurable disease as defined per recist v.1.1 or bone-only disease. - tumor lesions previously irradiated or subjected to other locoregional therapy will only be deemed measurable if disease progression at the treated site after completion of therapy is clearly documented.

her2-positive tumor as defined by documentation of erbb-2 gene amplification by fish (as defined by a her2/cep17 ratio ≥2) or chromogenic in situ hybridization (cish, as defined by the manufacturer's kit instruction) or documentation of her2 overexpression by ihc (defined as ihc3+, or ihc2+ with fish or cish confirmation) based on local laboratory results

patients with advanced, symptomatic, visceral spread, that are at risk of life-threatening complications in the short term (including patients with massive uncontrolled effusions [pleural, pericardial, peritoneal], pulmonary lymphangitis, and over 50% liver involvement).