Anti-HER2 Therapy + Fulvestrant/Capecitabine in Women With HR+, HER2+, Non-visceral Metastases Stage IV Breast Cancer

This is a prospective, randomized, 2-arm, multicenter study to compare the safety and efficiency of anti-HER2 therapy (Trastuzumab ± Pertuzumab) plus fulvestrant versus anti-HER2 therapy (Trastuzumab ± Pertuzumab) plus capecitabine in women with hormone receptor positive (HR+), human epidermal growth factor receptor 2 positive (HER2+), non-visceral metastases, stage IV breast cancer. Subjects will be randomized into one of two treatment arms. Arm A subjects will receive the anti-HER2 therapy plus fulvestrant. Arm B subjects will receive the anti-HER2 therapy plus capecitabine. The use of Pertuzumab depends on patients' choices.