SAN ANTONIO—Despite limited data, neoadjuvant endocrine therapy appears to improve surgical outcomes and “to be as effective as chemotherapy in converting mastectomy to lumpectomy,” according to Cynthia X. Ma, MD, PhD, of Washington University in St. Louis, MO. Dr Ma spoke at the 2015 San Antonio Breast Cancer Symposium.1

“Neoadjuvant endocrine therapy can improve surgical outcome, predict individual relapse risk, and provide a research platform to investigate mechanisms of endocrine responsiveness and novel drug development,” Dr Ma said.

Research has shown that that women who were initially ineligible for breast conservation surgery became eligible after neoadjuvant endocrine therapy with tamoxifen or aromatase inhibitors like letrozole, she said, noting that the aromatase inhibitors appear to be equivalent to one another in this regard.

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“Neoadjuvant endocrine therapy has become a standard approach in clinical practice to improve the chances of breast conservation in postmenopausal women with locally advanced estrogen receptor positive breast cancer, based on results from several neoadjuvant endocrine trials,” she said.

Neoadjuvant endocrine therapy also allows early assessments of tumor responsiveness to endocrine therapy—allowing oncologists to tailor adjuvant treatments to their individual patients.

The optimal duration of neoadjuvant endocrine therapy “has really not been investigated,” she noted. However, “on-treatment Ki67 at 2 weeks predicts relapse risk” following neoadjuvant endocrine therapy.

The IMPACT study showed that anastrozole was superior to tamoxifen in Ki67 suppression and ATAC showed that anastrozole was associated with superior disease-free survival compared to tamoxifen.

That makes Ki67 a very appealing clinical research biomarker—but before Ki67 can be adopted as a biomarker for daily clinical practice, more must be understood in regards to variation in preanalytical, analytical, and storage variations between testing labs, she cautioned.

RELATED: Tamoxifen, Anastrozole Chemoprevention Reduces Invasive Breast Cancer Risk

“Persistent cell proliferation on neoadjuvant endocrine therapy predicts a high risk of early relapse, for whom novel treatment strategies are in great need,” Dr Ma explained. “In contrast, the Preoperative Endocrine Prognostic Index (PEPI) score of 0 (pathologic pT1/2, pN0, Ki67 ≤ 2.7% ER Allred 3-8) in response to neoadjuvant endocrine therapy is being prospectively evaluated in the ongoing Alliance A011106 (ALTERNATE) as a marker of endocrine sensitive disease, for whom chemotherapy could be avoided.”


  1. Ma, CX. Neoadjuvant endocrine therapy. Oral presentation at: San Antonio Breast Cancer Symposium 2015; December 8, 2015; San Antonio, TX.