Ovarian Function Suppression Plus Aromatase Inhibitors or Tamoxifen in Premenopausal HR-positive Breast Cancer

Breast cancer is the most common type of malignant tumor in women, accounting for 30% of women’s cancer, while the mortality rate ranks second among women’s cancer [1]. Twenty-five percent of all breast cancer patients are premenopausal patients, and 7% of patients are younger than 40 years old [2]. According to statistics analysis, nearly 60% of premenopausal breast cancer patients aging 15-39 years old are HR-positive [3]. Adjuvant endocrine therapy plays an increasingly important role in these patients due to its high efficiency and low toxicity. It is an important means to reduce the risk of recurrence of these patients. 5-10 years tamoxifen (TAM) treatment is the gold standard for adjuvant endocrine therapy in premenopausal hormone receptor (HR) positive breast cancer patients [4-9]. Since the discovery of aromatase inhibitors (AIs), various clinical studies [10-13] have proved that AIs are better than TAM for adjuvant treatment of early postmenopausal breast cancer, and AIs have become the first-line therapy for postmenopausal women with early breast cancer. Ovarian function suppression (OFS) has been used in the treatment of breast cancer for decades. Earlier studies have confirmed that OFS alone can reduce the risk of recurrence of premenopausal breast cancer patients and improved survival [14-15]. A multicenter retrospective cohort study of premenopausal women with stage I to III hormone receptor-positive breast cancer diagnosed from 2006 to 2015 showed in the real-world setting that after 2014, the number of people using OFS increased. 25% menopausal patients used OFS, of which more than 30% of patients used OFS plus an aromatase inhibitor (AI) [16]. OFS application adds benefits to TAM as a study demonstrated that when compared with using of TAM alone, the addition of OFS to TAM reduces the patient’s estradiol level, and at the same time significantly reduces the patient’s breast density and endometrial thickness [17]. The application of OFS also makes AIs applicable to premenopausal women. Generally speaking, AIs are not used in premenopausal patients, because ovarian function will increase the production of aromatase, causing AIs to lose efficacy. After using Als in postmenopausal patients, the estrogen concentration of the patients may not be detectable [18]. Premenopausal patients using exemestane in addition to Abstract