Anastrozole and Letrozole After Surgery for the Treatment of Stage I-III Breast Cancer

Inclusion Criteria:

REGISTRATION-INCLUSION CRITERIA

Disease characteristics:

Histological confirmation of invasive breast carcinoma
Stage I-III breast cancer
Estrogen receptor (ER) positive disease according to American Society of Clinical Oncology (ASCO)/College of American Pathologists (CAP) guidelines as ER >= 1% positive nuclear staining

Completion of all planned cancer treatments prior to registration:

Surgical resection of breast and nodal surgery; (NOTE: Reconstructive surgery does not have to be completed)
Adjuvant radiation therapy, if needed
Neoadjuvant and/or adjuvant chemotherapy, if needed

Post-menopausal defined as

Age >= 60 and amenorrhea > 12 consecutive months OR
Previous bilateral oophorectomy OR

Age < 60 and amenorrhea > 12 consecutive months and documented follicle stimulating hormone (FSH) level within post-menopausal range according to institutional standard

NOTE: Patients who did not meet these criteria at time of diagnosis and received pre-operative (neoadjuvant) or post-operative (adjuvant) chemotherapy will not be allowed to participate
Eastern Cooperative Oncology Group (ECOG) performance status (PS) 0, 1, or 2
Hemoglobin >= 8.0 g/dL (obtained =< 14 days prior to registration)
Absolute neutrophil count (ANC) >= 1500/mm^3 (obtained =< 14 days prior to registration)
Platelet count >= 70,000/mm^3 (obtained =< 14 days prior to registration)
Total bilirubin =< 1.5 x upper limit of normal (ULN) (obtained =< 14 days prior to registration)
Alanine aminotransferase (ALT) and aspartate transaminase (AST) =< 3 x ULN (obtained =< 14 days prior to registration)
Ability to swallow oral medication
Provide written informed consent
Willingness to provide mandatory blood specimens for correlative research
Willing to return to enrolling institution for follow-up (during the Active Monitoring Phase of the study)
RE-REGISTRATION-INCLUSION CRITERIA
Confirmation that baseline blood sample was drawn and submitted

Blood estrogen levels after cycle 1 anastrozole (ANA1) must meet the following criteria:

E1 >= 1.3 pg/ml, AND
E2 >= 0.5 pg/ml

Exclusion Criteria:

REGISTRATION-EXCLUSION CRITERIA
Pre-menopausal women receiving ovarian function suppression (goserelin, leuprolide, etc.)
Stage IV (metastatic) breast cancer

HER2 positive breast cancer as defined by

HER2 immunohistochemistry (IHC) >= 3+
HER2/CEP17 >= 2.0
HER2/CEP17 < 2.0 and average HER2 copy number of >= 6.0 signals/cell

Prior endocrine therapy for this breast cancer. Exceptions:

Pre-operative aromatase therapy (anastrozole, letrozole, or exemestane) and last treatment was >= 4 weeks prior to registration OR
Pre-operative tamoxifen therapy and last treatment was >= 12 weeks prior to registration

Currently receiving any of the following cancer-directed therapies:

Radiation therapy
Systemic therapy such as chemotherapy (standard or investigational)

Bisphosphonate therapy started < 4 weeks prior to registration

NOTE: If patient is currently on bisphosphonate therapy she must be on stable dose for >= 4 weeks prior to registration. Patients not currently taking bisphosphonates will be allowed to start bisphosphonate therapy after completion of anastrozole (1 mg and 10 mg daily [if given]). Information regarding bisphosphonate therapy will be collected
Current use of systemic or topical exogenous estrogen or progesterone (menopausal hormone replacement therapy [HRT])
Prior ovarian function suppression (leuprolide, goserelin, etc.)
Inability to provide informed consent

History of contralateral ductal carcinoma in situ (DCIS) or invasive breast cancer

NOTE: Exception allowed if

Patient did not receive adjuvant endocrine therapy OR
Patient received adjuvant endocrine therapy but has been off treatment for at least 6 months prior to registration

Concurrent active malignancy or history of malignancy =< 3 years prior to registration

NOTE: Exceptions allowed for successfully treated cervical carcinoma in situ, lobular carcinoma in situ of the breast, papillary thyroid cancer, or non-melanoma skin cancer
Prior prevention therapy with an aromatase inhibitor or a selective estrogen receptor modulator (SERM). Exception: Therapy with a SERM (tamoxifen or raloxifene) is allowed if patient has been off treatment for >= 6 months prior to registration