Neoadjuvant chemotherapy (NAC) is the first line treatment for locally advanced breast cancer (BC). Besides making breast conserving surgery feasible, its main aim is to achieve a pathological complete response (pCR). Previous studies demonstrated that a pCR correlated with a higher disease-free survival. Tumor response may vary among different BC subtypes and only 30% of BC respond completely to NAC. Treating chemo-resistant disease with NAC may cause patient harm due to drug toxicity and surgery delay. It is therefore very important to promptly identify those women who will not benefit from NAC. Mammography and ultrasound proved ineffective in monitoring changes in lesion size due to therapy-induced fibrosis. MRI is the most accurate imaging technique for assessing early clinical response by measuring tumor size, however its accuracy is lower post NAC. This necessitates the need for a new technique able to non invasively assess the effectiveness of NAC. Optical techniques are sensitive to the biological changes that occur within the tumor after NAC administration. These changes occur prior to tumor size reduction. Optically estimated total hemoglobin concentration correlates with the histological analysis of vasculature as well as with tumor-associated angiogenesis which can affect tumor changes during NAC. Other promising biomarkers related to tissue composition (water, lipid, collagen content) and structure (scattering) may also be evaluated by optical techniques. The aim of the study is to monitor the effectiveness of NAC in BC patients with a near infrared spectroscopic imaging platform which allows to non-invasively detect changes in vascularization and size of BC and to characterize the presence of temporal changes in regional concentrations of relevant biomarkers (oxy- and deoxyhemoglobin, water, lipid and collagen concentration, scattering) within tissue during NAC. This optical imaging technique will provide a non-invasive, safe and relatively inexpensive tool to monitor patients' response to NAC and to predict their outcome.