Lapatinib and Tamoxifen in Treating Patients With Locally Advanced or Metastatic Breast Cancer That Did Not Respond to Previous Tamoxifen

PRIMARY OBJECTIVES: I. To determine the response rate (complete response and partial response) of tamoxifen (tamoxifen citrate) and GW572016 (lapatinib ditosylate) in women with hormone refractory, metastatic breast cancer. II. To describe the changes in phosphorylation of epidermal growth factor receptor (EGFR), human EGFR 2 (her2), protein B kinase (AKT) kinase, mitogen activated protein kinase (MAPK), estrogen receptor (ER)-Serine (Ser) 118, and ER-Ser167 in tumor tissue after administration of tamoxifen and GW572016. OUTLINE: Patients receive lapatinib ditosylate orally (PO) daily and tamoxifen citrate PO daily. Courses repeat every 28 days in the absence of disease progression or unacceptable toxicity. After completion of study treatment, patients are followed up at 1 month and then every 3 months thereafter.