Fulvestrant or Tamoxifen Citrate in Treating Patients with Cyclin D1 and Estrogen Receptor Positive Breast Cancer

Inclusion Criteria

• Written informed consent prior to beginning specific protocol procedures, including expected cooperation of the patients for the study treatment regimen and follow-up, must be obtained and documented according to the local regulatory requirements
• Eastern Cooperative Oncology Group (ECOG) performance status (PS) 0-2
• New diagnosis of invasive cyclin D1 +, estrogen receptor (ER)+, progesterone receptor (PR) +/-, Her2- breast cancer * Cyclin D1 positive as defined as a total immunohistochemical score of 5 or greater * Hormone receptor positive as defined as >= 10% positive stained cells * HER2-normal (immunohistochemistry [IHC] score 0-1 or fluorescence in situ hybridization [FISH] negative [in-situ hybridization (ISH) ratio =< 2.0 status])
• Tumor size at least 5 mm with planned primary surgery at Mount Sinai
• A negative urine dipstick pregnancy test

Exclusion Criteria

• Postmenopausal women * Postmenopausal if satisfies one or more of the following criteria: age greater than 52 years of age; having had a bilateral oophorectomy; amenorrhoeic for at least 12 months
• Estrogen receptor negative invasive breast carcinoma as defined as less than 10% stained cells
• Prior antiestrogen therapy
• Tumor size less than 5 mm
• Prior diagnosis of thrombosis or known hypercoagulable state
• Known history of bleeding diathesis
• Known liver disease
• Prior treatment with neoadjuvant therapy
• Inflammatory breast cancer defined as clinically significant erythema of the breast and/or documented dermal lymphatic invasion (not direct skin invasion by tumor or peau d’orange without erythema)
• Current severe or uncontrolled systemic disease
• Pregnancy or lactation period; patients of childbearing potential must implement adequate non-hormonal contraceptive measures (barrier methods, intrauterine contraceptive devices) during study treatment
• Prior malignancy (including invasive or ductal in-situ breast cancer) within 5 years prior to randomization, except curatively treated basal cell carcinoma of the skin and carcinoma in situ of the cervix