in: Breast Cancer : A Guide to Clinical Practice, Adnan AydinerAbdullah IgciAtilla Soran, Editor, Springer, London/Berlin , London, pp.413-432, 2019
Adjuvant endocrine therapy should be administered to patients with ER-positive and/or PR-positive invasive breast cancer, regardless of HER2 status, patient age, or cytotoxic therapy provided. Endocrine therapy can be initiated either with or after radiotherapy. Tamoxifen is the standard adjuvant endocrine therapy in women who are premenopausal at the time of diagnosis. Ovarian function suppression (OFS) might be added to tamoxifen in some patients younger than 35 years. In high-risk premenopausal patients with multiple poor prognostic factors, OFS plus an aromatase inhibitor (AI) may be a treatment option. The adjuvant tamoxifen treatment duration may be prolonged to 10 years in high-risk patients. In postmenopausal women, both tamoxifen and AIs may be valid endocrine therapy options. In high-risk postmenopausal patients with multiple poor prognostic factors, AI may be the best treatment option. An AI provided for a total of 5 or more years, an AI provided for 2–3 years followed by tamoxifen to complete 5 years of adjuvant endocrine therapy, and tamoxifen provided for 2–3 years followed by an AI to complete 5–8 years of endocrine therapy are all adjuvant treatment options. Tamoxifen for 4.5–6 years followed by 5 years of an AI or tamoxifen for up to 10 years is also an option. Extending AI treatment beyond 5 years in postmenopausal women can be recommended for high-risk patients.