Exemestane With Sunitinib (SUTENT®) in Metastatic Breast Cancer

The investigators want to find out if the treatments used in this study are helpful to patients that are diagnosed with hormone receptor positive metastatic breast cancer. The investigators want to also look at any side effects that could happen while patients are on the study treatments. The investigators want to see if there are any changes that could show us if your cancer is responding to the study treatments.

The study design is a phase II design. Eligible patients will undergo staging work up and start treatment. Every 28-day period (4 weeks) will count as a cycle. Medical evaluations will be performed every 4 weeks and staging work up will be repeated every 12 weeks. The primary objective of the study is to assess progression free survival (PFS) of treatment with exemestane and sunitinib in post¬menopausal subjects with hormone receptor positive (ER-positive and/or PR-positive) unresectable locally advanced or metastatic breast cancer subjects who have progressed on prior hormonal treatment. In addition we want to: 1. Obtain assessments of overall response rate (ORR), clinical benefit rate (CBR), and overall survival (OS). 2. Determine the safety and tolerability of the combination regimen. 3. Study molecular changes in tissue biopsies, circulating tumor cells (CTCs), and circulating endothelial cells (CECs), and explore associations with treatment response and resistance. 1\. Blood samples will be drawn for enumeration and profiling of circulating tumor cells and circulating endothelial cells at study entry (prior to starting study medications), four weeks after starting study medications, twelve weeks after starting study medications and at disease progression. These samples will be strongly encouraged but the patients may decline any or all of them without impacting their eligibility or continuation on the study. 2\. If the patient participating on the study has an easily accessible breast mass or metastatic lesion (e.g. lymphadenopathy, skin metastasis, chest wall metastasis), a core needle or punch biopsy will be obtained at study entry (prior to starting study medications), four weeks after starting study medications, and at disease progression. These biopsies will be strongly encouraged but the patients may decline any or all of them without impacting their eligibility or continuation on the study.