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