Breast cancer patients often undergo neoadjuvant chemotherapy to reduce the size of the tumor before surgery. Tumors which demonstrate a pathologic complete response associate with improved disease-free survival; however, as low as 10% of patients may achieve this status. The goal is to predict response to anti-cancer therapy early, so as to develop personalized treatments and optimize the patient’s results. Previous studies have shown that tumor response can be predicted within a few days of treatment initiation. We have developed a diffuse optical tomography (DOT) imaging system for monitoring the response of breast cancer patients to neoadjuvant chemotherapy. Our breast imaging system is a continuous wave system that uses four wavelengths in the near-infrared spectrum (765 nm, 808 nm, 827 nm, and 905 nm). Both breasts are imaged simultaneously with a total of 64 sources and 128 detectors. Three dimensional reconstructions for oxy-hemoglobin concentration ([HbO2]), deoxy-hemoglobin ([Hb]) concentrations, and water are performed using a PDE-constrained multispectral imaging method that uses the diffusion approximation as a model for light propagation. Each patient receives twelve weekly treatments of Taxane followed by four cycles of Doxorubicin and Cyclophosphamide (AC) given every other week. There are six DOT imaging time points: baseline, week 3 and 5 of Paclitaxel, before cycle 1 and 2 of AC, and before surgery. Preliminary results show that there is statistical significance for the percent change of [HbO2], [Hb], [HbT], and percent water at week 2 from the baseline between patients with a pathologic response to chemotherapy.