Adjuvant endocrine therapy should be considered in patients with invasive breast cancer that is estrogen or progesterone receptor positive, regardless of age, lymph node status, HER-2 status, or whether adjuvant chemotherapy has been applied. HER-2 overexpression is a marker of relative resistance to endocrine therapy. Tamoxifen is the most definitive endocrine therapy for the treatment of premenopausal and postmenopausal breast cancer patients. Adjuvant tamoxifen therapy can reduce annual recurrence rates by 39% and annual mortality by 31%. Tamoxifen should be administered after sequential chemotherapy. In international multicenter randomized controlled studies, ATAC demonstrated better efficacy of 5 years of anastrozole than 5 years of triamcinolone, BIG 1-98 demonstrated better efficacy of 5 years of triamcinolone than 5 years of triamcinolone, and MA-17 demonstrated further efficacy of 5 years of triamcinolone followed by 5 years of triamcinolone. And the IES-031 study demonstrated that sequential use of exemestane after 2-3 years of triamcinolone therapy significantly improved efficacy and improved patient prognosis over continued triamcinolone. The initiation of a new generation of aromatase inhibitors at different stages of postmenopausal adjuvant endocrine therapy has resulted in better outcomes, and these studies challenge the therapeutic status of 5 years of triamcinolone acetonide. 1. Endocrine therapy for premenopausal breast cancer For premenopausal breast cancer patients, the anti-estrogenic drug tamoxifen is preferred after 2-3 years of oral administration, and further treatment strategies are decided according to the patient’s FSH and estradiol levels. Patients with hormone levels up to postmenopausal choose to prefer oral third-generation aromatase inhibitors (anastrozole, letrozole, exemestane) up to 5 years; or choose to continue tamoxifen up to 5 years followed by sequential third-generation aromatase inhibitors for 5 years. Patients with premenopausal hormone levels choose to continue oral tamoxifen for up to 5 years, followed by sequential third-generation aromatase inhibitors for 5 years if FSH and estradiol levels reach menopausal levels; if hormone levels remain premenopausal, no further endocrine therapy is recommended. For premenopausal breast cancer patients with low risk of recurrence, who are young and have fertility requirements, a treatment regimen of pharmacologic ovarian debulking (goserelin) combined with a third-generation aromatase inhibitor administered orally for 5 years may be used. For premenopausal breast cancer patients with high risk of recurrence, a 5-year oral treatment regimen with third-generation aromatase inhibitors is recommended after ovariectomy debulking. 2.Endocrine therapy for postmenopausal breast cancer Determination of menopause is the cornerstone of choosing endocrine therapy drugs for breast cancer. Menopause generally refers to the permanent termination of menstruation and is also used to describe the persistent reduction of ovarian synthesis of estrogen during breast cancer treatment. With regard to menopause, it is clearly defined as: after bilateral oophorectomy; age ≥ 60 years; age < 60 years, menopause ≥ 12 months, not receiving chemotherapy, tamoxifen, toremifene or ovarian function suppression therapy, and FSH and estradiol levels are within the postmenopausal range; age < 60 years of age, are taking tamoxifen or toremifene, and FSH and estradiol levels should be within the postmenopausal range. Menopause cannot be determined in patients receiving LH-RH agonists or antagonists; in premenopausal women receiving adjuvant chemotherapy, menopause cannot be used as a basis for determining menopause; because although patients may stop ovulating or experience menopause after chemotherapy, ovarian function may still be normal or have the potential to recover. In women with chemotherapy-induced menopause who are considered for endocrine therapy with an aromatase inhibitor, this requires ovariectomy or serial testing of FSH and/or estradiol levels to ensure that the patient is in a postmenopausal state. Results from multiple clinical trials confirm that the application of third-generation aromatase inhibitors to postmenopausal hormone receptor-positive breast cancer patients, whether as initial adjuvant therapy, sequential therapy, or subsequent intensive therapy, reduces the risk of recurrence, including the risk of ipsilateral recurrence, contralateral breast cancer, and distant metastases, compared to tamoxifen alone. Tamoxifen alone for 5 years is limited to those who do not receive aromatase inhibitors or have contraindications to aromatase inhibitors. For postmenopausal breast cancer patients, adjuvant endocrine therapy with a third-generation aromatase inhibitor is preferred orally for 5 years. A treatment regimen of oral tamoxifen for 2-3 years followed by sequential third-generation aromatase inhibitors for up to 5 years or oral tamoxifen for 5 years followed by sequential third-generation aromatase inhibitors for 5 years is also available. For patients with contraindications to aromatase inhibitors or unable to receive aromatase inhibitors, or unable to tolerate aromatase inhibitors, oral tamoxifen may be administered for 5 years. Many premenopausal and postmenopausal patients with hormone-responsive breast cancer can benefit from sequential endocrine therapy when their disease progresses. Treatment for premenopausal women includes LHRH agonists, surgical or radiation oophorectomy, progesterone analogs, androgens (fluoxymesterone), and large amounts of estrogens (ethinyl estradiol). Endocrine therapy in postmenopausal patients includes selective non-steroidal aromatase inhibitors (anastrozole and letrozole), steroidal aromatase inhibitors (exemestane), fulvestrant, progesterone analogs, androgens and large amounts of estrogens.