Trial to Evaluate the Therapeutic Benefit of Fulvestrant in Combination With ZACTIMA in Postmenopausal Women With Bone Predominant, Hormone Receptor Positive Metastatic Breast Cancer

The purpose of this study is to evaluate whether the combination of fulvestrant and ZACTIMA, versus fulvestrant plus placebo, results in a significant decrease in the bone marker, urinary N-Telopeptide (NTx) in postmenopausal women with bone only, or bone predominant, hormone receptor-positive metastatic breast cancer. A significant decrease will be defined as a \> 30% reduction in urinary NTx level from baseline.

Tumor angiogenesis is associated with invasiveness and the metastatic potential of various cancers. Vascular endothelial growth factor (VEGF), the most potent and specific angiogenic factor, regulates normal and pathologic angiogenesis. The increased expression of VEGF has been correlated with metastases, recurrence and poor prognosis in many cancers. It has been shown the VEGF is involved in osteolysis in women with bone metastases. ZACTIMA is an agent which targets VEGF. ZACTIMA is a new agent with novel method of action - it is a VEGF inhibitor, epidermal growth factor (EGFR) inhibitor, tyrosine kinase inhibitor, as well as a potential RET kinase activity inhibitor. In summary, women with bone only, or bone predominant, metastatic breast cancer is an ideal group to study anti-angiogenic therapies where angiogenesis could be a major factor in tumor progression and where anti-angiogenic treatment with agents like ZACTIMA could be more effective.