Breast cancer is still the number one malignant tumor among women, and the incidence is especially high in developed cities such as Shanghai. Endocrine therapy plays an important role in the treatment of breast cancer cancer after radical surgery. Estrogen is a type of hormone in the body that has many functions, including triggering female sexual characteristics and reproduction. Some cells in the breast will have estrogen receptors and they will be activated by estrogen. If a tumor cell in the breast has estrogen receptors, then it is estrogen receptor positive, or ER+ for short, otherwise it is estrogen receptor negative. Studies have proven that ER+ patients will generally benefit from endocrine therapy, which refers to the inhibition of tumor cell growth by lowering estrogen levels in the body or inhibiting the effects of estrogen. The main drugs are: tamoxifen (triamcinolone), anastrozole Endocrine therapy for ER+ breast cancer is currently recommended for 5-10 years, but studies have shown that extended endocrine therapy after 5 years will only benefit 2-3% of patients, while more than half of patients start to experience various adverse drug reactions during the course of treatment, with serious complications of endometrial cancer and pulmonary embolism (about 1%). The Breast Cancer Index (BCI) is the latest second-generation marker for breast cancer recurrence and is considered the only marker that can predict prolonged endocrine therapy, based on pathological sections of surgically resected tumors. The test is covered by health insurance in the United States and has just recently entered the domestic market, but currently only the test is performed in China, and there is no certified institution for data analysis, which needs to be transmitted to the United States and then performed.