This summary table contains detailed information about research studies. Summary tables offer an informative look at the science behind many breast cancer guidelines and recommendations. However, they should be viewed with some caution. In order to read and interpret research tables successfully, it is important to understand some key concepts. Learn how to read a research table.
Introduction: Hormone therapy is a standard part of treatment for hormone receptor-positive breast cancers (estrogen and/or progesterone receptor-positive cancers). It is not used to treat hormone receptor-negative breast cancer. Hormone therapies include tamoxifen and aromatase inhibitors.
In some cases, hormone therapy may be given before breast surgery (called neoadjuvant hormone therapy). Neoadjuvant therapy may reduce the size of a tumor enough that a lumpectomy becomes an option to a mastectomy. Early study results show neoadjuvant hormone therapy may benefit some women with stage II or stage III hormone receptor-positive breast cancers. Findings to date are mainly from studies of women 70 years and older. For women in this age group, some standard treatments (surgery and/or chemotherapy) may not be recommended for health reasons. Neoadjuvant hormone therapy with aromatase inhibitors may offer more benefit and fewer serious side effects than tamoxifen [1-4].
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.
Study Population(number of participants)
Type ofAromatase Inhibitor
Duration ofNeoadjuvant Treatment
Clinical Response andRate of Lumpectomy with Neoadjuvant Aromatase Inhibitor vs. Neoadjuvant Tamoxifen
Randomized Clinical Trials
Ellis et al. andEiermann et al. [1,2]
Clinical response:letrozole = 55% vs. tamoxifen = 36%
Lumpectomy:letrozole = 45% vs. tamoxifen = 35%
PROACT Trial 
Clinical response: anastrozole = 50% vs. tamoxifen = 40% Lumpectomy:anastrozole = 43% vs. tamoxifen = 31%
Ellis et al. 
Clinical response:letrozole = 60% vs. tamoxifen = 41%
Lumpectomy:letrozole = 48% vs. tamoxifen = 36%
IMPACT Trial 
Clinical response: anastrozole = 37% vs. tamoxifen = 36% Lumpectomy:anastrozole = 44% vs. tamoxifen = 31%
Clinical Response and Rate of Lumpectomy with Neoadjuvant Aromatase Inhibitor
Ellis et al. 
Anastrozole, exemestane or letrozole
1. 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.
2. 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.
3. 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.
4. 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.
5. 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.
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