Anti-angiogenic therapy represents a major step forward in breast cancer care. Further development of such therapies relies on the availability of predictive biomarkers of vascular mediated changes including hypoxia and vascular volume. Optical spectroscopy is a promising tool for fast, non-invasive measurements of tumor hypoxia and vascular volume. Our objective is to exploit the chemically specific and quantitative capabilities of this non-invasive technology to monitor vascular mediated changes in breast cancer in response to molecular and chemotherapy and correlate it to biological endpoints (tissue immuno histochemical assays) and clinical endpoints. We will demonstrate the feasibility and effectiveness of our novel approach in pre-clinical models of breast cancer and pilot clinical studies on patients with breast disease.