Tamoxifen Citrate in Treating Patients With Metastatic or Recurrent Breast Cancer

Inclusion Criteria: * Histologically confirmed adenocarcinoma of the breast * Stage III (locally advanced), metastatic, or recurrent disease * Deemed not resectable * Estrogen-receptor and/or progesterone-receptor positive disease * Receptor status is based on most recent results * Measurable or non-measurable disease * ECOG performance status 0-2 * History of central nervous system (CNS) metastasis allowed provided it has been treated (surgery, radiotherapy, or radiosurgery) within the past 4 weeks and does not require medications to control symptoms * Total bilirubin ≤ 1.5 times upper limit of normal (ULN) * Alanine transaminase (ALT) and aspartate transaminase (AST) ≤ 2.5 times ULN (≤ 5 times ULN if liver metastases present) * Negative pregnancy test * Fertile patients must use effective nonhormonal contraception * Disease-free of prior invasive malignancies for ≥ 5 years with the exception of curatively-treated basal cell or squamous cell carcinoma of the skin or carcinoma in situ of the cervix * Prior chemotherapy, trastuzumab, or bevacizumab in the adjuvant setting allowed provided it has been completed ≥ 4 weeks before study therapy; other prior non-hormonal investigational agents in the adjuvant setting must have been completed at least 4 weeks prior to study registration and should be discussed with the study PI * Prior tamoxifen as adjuvant treatment is allowed as long as the patient did not have disease relapse or progression while on adjuvant tamoxifen or within 4 weeks of last dose * Treatment in the advanced setting must have been completed at least 2 weeks prior to study initiation * Prior aromatase inhibitors (e.g., anastrozole, letrozole, exemestane, aminoglutethamide) are allowed in the adjuvant or metastatic setting * At least 2 weeks since prior and no concurrent medications that are strong to moderate inhibitors of CYP2D6 and may alter tamoxifen citrate metabolism including, but not limited to, any of the following: * Paroxetine (Paxil) * Fluoxetine (Prozac) * Bupropion (Wellbutrin) * Quinidine (Cardioquin) * Concurrent radiotherapy to painful sites of bone disease or areas of impending fractures allowed provided the following criteria are met: * Radiotherapy was initiated before study entry * Sites of measurable or non-measurable disease are outside the radiotherapy port * Recovered from prior radiotherapy Exclusion Criteria: * Pregnant or nursing * Concurrent chemotherapy * Leptomeningeal disease * Non-protocol concurrent hormonal therapy * Medical or psychiatric conditions that would interfere with protocol compliance, the ability to provide informed consent, assessment of response, or anticipated toxicities * Prior tamoxifen for advanced disease * More than 2 lines of non-hormonal treatment in the locally advanced or metastatic setting, including trastuzumab (Herceptin), bevacizumab, or other biologics * Starting bisphosphonate therapy while receiving treatment on this study * Patients who have begun receiving bisphosphonate therapy prior to registration may continue at the same intervals used prior to study registration