Research table: Neoadjuvant hormone therapy for estrogen receptor-positive breast cancer
This summary table contains detailed information about research studies. Summary tables are a useful way to look at the science behind many breast cancer guidelines and recommendations. However, to get the most out of the tables, it’s important to understand some key concepts. Learn how to read a research table.
Introduction: Hormone therapy is a standard treatment for hormone receptor-positive breast cancers (estrogen and/or progesterone receptor-positive cancers). It’s not used to treat hormone receptor-negative breast cancers.
Hormone therapy may be given before breast surgery (called neoadjuvant hormone therapy) to try to shrink the tumor enough so a lumpectomy becomes an option to a mastectomy.
Neoadjuvant hormone therapy is a treatment option for some postmenopausal women, including those who can’t have chemotherapy due to health problems or advanced age, and for some women who have a very low risk of breast cancer recurrence .
For postmenopausal women, neoadjuvant hormone therapy with an aromatase inhibitor appears to offer more benefit and fewer serious side effects than with tamoxifen [2-5].
Learn more about neoadjuvant hormone therapy.
Learn about the strengths and weaknesses of different types of studies.
Study selection criteria: Phase III randomized clinical trials with 100 or more participants.
Clinical Response and
Randomized Clinical Trials
Ellis et al. and
PROACT Trial 
Ellis et al. 
IMPACT Trial 
Clinical Response and
Ellis et al. 
Anastrozole, exemestane or letrozole
anastrozole = 69%
exemestane = 63%
letrozole = 75%
- National Comprehensive Cancer Network (NCCN). NCCN Clinical practice guidelines in oncology: Breast cancer V.1.2022. http://www.nccn.org/, 2021.
- Ellis MJ, Coop A, Singh B, et al. Letrozole is more effective neoadjuvant endocrine therapy than tamoxifen for ErbB-1- and/or ErbB-2-positive, estrogen receptor-positive primary breast cancer: evidence from a phase III randomized trial. J Clin Oncol. 19(18):3808-16, 2001.
- Eiermann W, Paepke S, Appfelstaedt J, et al. for the Letrozole Neo-Adjuvant Breast Cancer Study Group. Preoperative treatment of postmenopausal breast cancer patients with letrozole: A randomized double-blind multicenter study. Ann Oncol. 12(11):1527-32, 2001.
- Cataliotti L, Buzdar AU, Noguchi S, et al. Comparison of anastrozole versus tamoxifen as preoperative therapy in postmenopausal women with hormone receptor-positive breast cancer: the Pre-Operative “Arimidex” Compared to Tamoxifen (PROACT) trial. Cancer. 106(10):2095-103, 2006.
- Smith IE, Dowsett M, Ebbs SR, et al. Neoadjuvant treatment of postmenopausal breast cancer with anastrozole, tamoxifen, or both in combination: the Immediate Preoperative Anastrozole, Tamoxifen, or Combined with Tamoxifen (IMPACT) multicenter double-blind randomized trial. J Clin Oncol. 23(22):5108-16, 2005.
- Spring LM, Gupta A, Reynolds KL, et al. Neoadjuvant endocrine therapy for estrogen receptor–positive breast cancer: a systematic review and meta-analysis. JAMA Oncol. 2(11):1477-1486, 2016.
- Ellis MJ, Suman VJ, Hoog J, et al. Randomized phase II neoadjuvant comparison between letrozole, anastrozole, and exemestane for postmenopausal women with estrogen receptor-rich stage 2 to 3 breast cancer: clinical and biomarker outcomes and predictive value of the baseline PAM50-based intrinsic subtype–ACOSOG Z1031. J Clin Oncol. 29(17):2342-9, 2011.