Pilot Study Estradiol Followed by Exemestane Hormone Receptor + Metastatic Breast Cancer

OBJECTIVES: I. To assess feasibility and toxicity associated with estradiol followed by exemestane in the treatment of estrogen receptor positive metastatic breast cancer patients failing prior aromatase inhibitor therapy. II. Exploratory analysis of bio-correlates which will evaluate the mechanism of action of this treatment combination: changes in serum M-30, a marker of mitochondrial apoptosis; changes in number of circulating tumor cells (CTC); changes in CTC expression of ER, IGF1-R, and M-30. III. Exploratory analysis of Progression Free Survival (PFS). OUTLINE: Patients receive oral therapeutic estradiol once daily on days 1-3, twice daily on days 4-7, and thrice daily on days 8-90. Beginning on day 98, patients receive oral exemestane once daily in the absence of disease progression or unacceptable toxicity. After completion of study treatment, patients are followed up periodically.