Phase II Study of Neoadjuvant ArOMatase Inhibitor Therapy for ER+ Breast Cancer (NAOMI)

This is a single-arm, open-label study testing the effects of neoadjuvant therapy with the aromatase inhibitor letrozole in post-menopausal women with Stage I-III ER+, HER2- breast cancer. Eligible subjects will be treated with letrozole therapy for 4 to 24 weeks prior to surgical resection of the tumor. Tumor specimens obtained at baseline (diagnostic biopsy) and at surgery (surgical specimen) will be compared using molecular analyses. A subset of subjects will be asked to provide an optional research tumor biopsy prior to treatment for molecular analysis. Subjects will be evaluated for treatment adherence and provide feedback via survey questionnaires to identify potential causes of non-adherence.

Approximately 70% of breast cancers express estrogen receptor alpha (ER), which is activated by estrogens and typically drives cancer cell growth. Adjuvant therapy with anti-estrogens such as tamoxifen and aromatase inhibitors (AIs) is commonly used to inhibit ER to prevent cancer (re)growth after early-stage breast tumors are surgically removed. However, \~33% of such patients (\~300,000 new cases per year worldwide) will eventually develop anti-estrogen-resistant breast cancer that is metastatic or locally advanced; at this stage, the disease is almost never cured using available therapies and is uniformly fatal. Therefore, more effective treatment early in the course of disease (i.e., in the adjuvant setting, shortly after surgical removal of a tumor) has huge potential to prevent cancer regrowth. Most often, ER+ breast cancers re-emerge in the years after the end of the standard five-year anti-estrogen treatment regimen (called 'late recurrence'). Recent data indicate that continued anti-estrogen therapy in patients who remain "disease-free" after five years of anti-estrogen therapy modestly prevents cancer recurrence. However, tumor cells are detectable in bone marrow of patients who are "disease-free." Thus, antiestrogen therapy in "disease-free" patients likely suppresses the growth of undetectable tumor cells, keeping them in a "clinically dormant" state (i.e., undetectable by standard clinical methods). Little is known about how such dormant cancer cells survive. This clinical study will help identify the signaling pathways essential for the survival of clinically dormant ER+ breast cancer cells to enable the development of more effective therapies to eradicate such cells and prevent cancer recurrence.

Eligibility Criteria:
Inclusion Criteria:

1. Histologic documentation of invasive breast cancer by core needle or incisional biopsy. Subjects without excess baseline tumor tissue are eligible and evaluable for Primary Objective #2 (re: adherence). Excess baseline biopsy tumor tissue sufficient to make ten 5- micron sections must be available for research use for a subject to be evaluable for Primary Objective #1 (re: molecular analyses).
2. The invasive cancer must be estrogen receptor alpha (ER)-positive, with ER staining present in greater than 50% of invasive cancer cells by IHC.
3. The invasive cancer must be HER2-negative (IHC 0-1+, or with a FISH ratio of \<1.8 if IHC is 2+ or if IHC has not been done).
4. Clinical Stage I-III invasive breast cancer with the intent to treat with surgical resection of the primary tumor. Baseline tumor must be ≥0.5 cm. For the optional research biopsy (from 5 subjects), tumor must be

   ≥1 cm.
5. Patients with multicentric or bilateral disease are eligible if the subject is a candidate for clinically indicated neoadjuvant endocrine therapy. Samples from all available tumors are requested for research purposes.
6. Women over 18 years of age, for whom (A) neoadjuvant treatment with an aromatase inhibitor would be clinically indicated, and (B) adjuvant treatment with one of the following would be clinically indicated: tamoxifen; anastrozole; letrozole. Women must be postmenopausal, defined as last menstrual period \>2 years prior to registration, or \>1 yearer prior to registration with FSH and estradiol in post-menopausal range.
7. Patients must meet the following clinical laboratory criteria:

   * Absolute neutrophil count (ANC) ≥ 1,000/mm3 and platelet count ≥ 75,000/mm3.
   * Total bilirubin ≤ 1.5 x the upper limit of the normal range (ULN).
   * Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) ≤ 3 x ULN.
8. Ability to give informed consent.

Exclusion Criteria:

1. Prior endocrine therapy for any histologically-confirmed cancer or prevention of breast cancer in the last 10 years is not allowed.
2. Any other neoadjuvant therapy for breast cancer. Bisphosphonate or denosumab treatment for metabolic bone issues are allowed.
3. Women who are pregnant or lactating.