Most breast cancers are hormone-dependent tumors, thus endocrine therapy has become an important part of comprehensive breast cancer treatment. Currently, endocrine therapy drugs commonly used for postmenopausal breast cancer patients include: anti-estrogens, progestins and aromatase inhibitors. The efficacy of endocrine therapy is related to hormone receptor status. Although triamcinolone acetonide (Tamoxifen, TAM) remains the standard of care for receptor-positive postmenopausal breast cancer patients, advances in aromatase inhibitors have provided new options for postmenopausal breast cancer patients. 1. Application of anti-estrogenic drugs The representative drug is triamcinolone acetonide. Triamcinolone is the most commonly used non-steroidal anti-estrogenic drug, which has been approved by FDA several years ago and become the first choice of endocrine therapy for premenopausal or postmenopausal ER receptor-positive breast cancer patients. Currently, it is the most widely used in endocrine treatment of breast cancer and has proven efficacy. Five years of adjuvant chemotherapy followed by triamcinolone acetonide remains the standard of care for patients with receptor-positive, postmenopausal breast cancer. Five years of oral triamcinolone acetonide reduces recurrence and mortality in breast cancer patients by 47% each, and halves the risk of contralateral breast cancer. Triamcinolone inhibits tumor cell growth primarily by competing with estrogen in the body for estrogen receptors in breast cancer cells. In addition, triamcinolone may also inhibit the growth of breast cancer cells by inhibiting tumor neovascularization and increasing the body’s cellular immunity. Triamcinolone is mainly metabolized by the liver and its side effects are mild, mainly flushing, itchy skin, muscle and joint pain, weakness, etc. A few patients have hypercalcemia. Patients are at risk of inducing venous thrombosis. Patients on long-term triamcinolone acetonide should have at least one to two uterine ultrasounds or endometrial biopsies per year for timely detection of endometrial tumors. Other similar drugs are Toremifen, a new anti-estrogen drug and inducer of triamcinolone with clinical efficacy equivalent to that of triamcinolone. It is indicated for the endocrine treatment of postmenopausal breast cancer patients. Some studies have shown that it is more effective in lung metastasis of breast cancer and can significantly reduce the number of ER receptors on breast cancer cell membranes, making it a new option for postmenopausal patients with progressive breast cancer. Toremifene has less effect on endometrial hyperplasia than triamcinolone and has no carcinogenic effect. Raloxifene (Raloxifene) is a selective estrogen receptor modulator. It has anti-estrogenic effects on the breast and uterus, while it has estrogen-like effects on the bone and cardiovascular systems and lipid metabolism, and is a selective ER receptor inhibitor. Some investigators have reported that raloxifene resulted in a reduced incidence of breast cancer in postmenopausal women. The side effects are less compared with triamcinolone acetonide. 2. Application of progestin drugs Progestin drugs mainly include megestrol and megestrol, which are most widely used. Progestin can lower IL-6 level in breast cancer patients, improve appetite, increase body weight, protect bone marrow, and thus improve the patient’s malignant state. Postmenopausal breast cancer cells can actively take up circulating estradiol and estrone. Megestrol and megestrol can promote the activity of intracellular sulfotransferase and progesterone dehydrogenase to change estradiol to estrone sulfate and estrone, thus diminishing the biological activity of estrogen. Progestins are generally used as second-line therapeutic agents after failure of triamcinolone therapy for endocrine treatment of recurrent or metastatic breast cancer. They are more effective in soft tissue and bone metastases. The side effects mainly include allergic reaction, obesity, breast swelling and pain, vaginal bleeding and increased secretion, etc. 3.Application of aromatase inhibitors The estrogen in postmenopausal women mainly comes from tissues other than the ovaries, and is made from androstenedione and testosterone through aromatization to become estrogen. Aromatase is an essential substance in this process. Aromatase inhibitors inhibit the activity of this enzyme and block the synthesis of estrogen, thereby controlling the growth of breast cancer cells and treating the tumor. Although both pre- and post-menopausal breast cancer patients can use triamcinolone acetonide as endocrine therapy, only post-menopausal breast cancer patients should be able to use aromatase inhibitors. A woman should be judged to be menopausal by one of the following criteria: 1. post bilateral oophorectomy; 2. menopause for at least 6 months after radiation therapy depot; 3. age 60 years or older. If less than 60 years of age, menopause must be spontaneous for at least 1 year; 4. And except for chemotherapy, triamcinolone acetonide, toremifene or due to ovarian suppression, follicle stimulating hormone (FSH) and plasma estradiol levels are in the postmenopausal range before menopause can be judged. The first-generation aromatase inhibitor amiloride has limited its clinical use due to its high side effects and the need for concomitant glucocorticoid application. Formestone is a representative drug of the second generation of aromatase inhibitors. It inhibits the activity of aromatase by binding to aromatase substrate binding sites in the body, thus reducing the blood estrogen level in postmenopausal breast cancer patients with rapid and long-lasting effects. However, because the drug is an injectable form, it can cause pain, inflammation and hardness at the injection site after long-term intramuscular injection. Therefore, aromatase inhibitors have evolved to third-generation oral formulations. Third-generation aromatase inhibitors include Letrozole (Letrozele), Anastrozole (Anatrzole), and Exemestane. Letrozele and anatrzole are non-steroidal, more potent than amiloride, and effective in patients with triamcinolone acetonide resistant breast cancer. Letrozole is highly specific in its inhibition of aromatase, with an effective rate of 10% to 36% in patients with advanced postmenopausal breast cancer who have failed previous therapy. Anastrozole is relatively selective in its action; it does not affect adrenocorticotropic hormone production. Exemestane is an irreversible, highly selective steroidal aromatase inactivator. It shows some efficacy in postmenopausal breast cancer patients who are resistant to triamcinolone. Its mechanism of action is to act directly on the aromatase active gene, so there is no cross-resistance with non-steroidal aromatase inhibitors. Clinical benefit can still be obtained with exemestane after letrozole and anastrozole treatment failure, and clinical benefit can be obtained with letrozole or anastrozole after exemestane treatment failure. Although 5 years of triamcinolone remains the gold standard for long-term adjuvant endocrine therapy for hormone receptor-positive breast cancer patients, several recent large-scale trials have reported better clinical benefit for postmenopausal breast cancer patients switching to third-generation aromatase inhibitors for 2 to 3 years of treatment over 5 years. Some investigators have also concluded that postoperative adjuvant therapy with third-generation aromatase inhibitors is superior to triamcinolone acetonide in reducing the rate of distant metastases and the risk of contralateral breast cancer, and that its safety profile can be assured. The main difference between the three aromatase inhibitors is that letrozole or anastrozole are reversible inhibitors and exemestane is an irreversible enzyme inactivator. Exemestane has androgen-like side effects; anastrozole has no effect on lipid metabolism; letrozole and exemestane affect lipid metabolism. The most common side effects of third-generation aromatase inhibitors are menopausal symptoms: flushing, vaginal dryness, skeletal muscle pain, and, to a lesser extent, effects on the endometrium. Long-term application of third-generation aromatase inhibitors with reduced estrogenic effects may lead to the development of osteoporosis and fractures. However, exemestane has no significant effect on bone metabolism.