Endocrine therapy forms the backbone of treatment for both early stage and advanced stage hormone receptor positive breast cancer. Although most patients with advanced estrogen receptor positive metastatic disease respond initially to endocrine therapies, this response is short lived. New therapies able to provide additional benefit to patients with hormone receptor positive, endocrine-resistant, advanced metastatic breast cancer are required. This study proposes to add lapatinib to endocrine therapy to treat hormone receptor positive HER-2 negative metastatic breast cancer patients.