A review of endocrine therapy in early estrogen receptor-positive breast cancer by St. Gallen Breast Cancer Conference 2021

Estrogen receptor (ER) positive (+) breast cancer is heterogeneous; thus, corresponding therapeutic regimens must differ according to the individual characteristics of ER+ breast cancer patients. At the 17th international St. Gallen Breast Cancer Conference (SG-BCC) in 2021, experts voted on numerous critical issues in relation to the use of neoadjuvant endocrine therapy (NET) and adjuvant endocrine therapy (AET) in the treatment of ER+ breast cancer. We interpreted the critical issues related to NET and AET according to the voting results of the 2021 SG-BCC and clinical practice in China. Specifically, we considered the following 8 points: (I) the selection of prognostic indicators for NET; (II) the selection of a NET population based on Ki-67; (III) the selection of polygenic testing combined with Ki-67 in the exemption of neoadjuvant chemotherapy; (IV) the selection of an AET population based on ER expression level and tumor size; (V) the selection of ovarian function suppression for a premenopausal population; (VI) the selection of early stage intensive AET for a postmenopausal population; (VII) the selection of an extended AET population; and (VIII) the selection of individuals exempt from chemotherapy. We combined the results of existing clinical studies to analyze the reasons why the experts at the 2021 SG-BCC voted on the above issues, and how clinicians should use the voting results of the 2021 SG-BCC poll to select therapeutic regimens for patients. Decisions to use ET to treat ER+ breast cancer patients should always balance individualized therapy and standardized therapy.