Optical tomography of breast cancer-monitoring response to primary medical therapy.

ABSTRACT

Diffuse optical imaging and spectroscopy use near-infrared light to derive physiological parameters such as total hemoglobin concentration and tissue oxygen saturation. Numerous clinical studies have been carried out, either using stand-alone optical methods or in combination with alternative imaging techniques. Studies have demonstrated that diffuse optical imaging and spectroscopy are able to distinguish malignant lesions from benign tissues. Breast cancer is characterized by an increase in total hemoglobin and a decrease in tissue oxygen saturation. Benign lesions such as cysts and fibroadenomas have also been studied, with less conclusive results. As diffuse optical imaging and spectroscopy do not use ionizing radiation, they are a suitable technique for performing repeated scans, such as for monitoring treatment response. This provides a unique functional and dynamic imaging method that reflects changes in tumor angiogenesis and hypoxia. When breast cancers are treated with primary medical therapy, this can result in a selective antiangiogenic effect that could help predict response to treatment earlier than by assessment of tumor size. Diffuse optical imaging and spectroscopy have been used to scan women at several points prior to and during their neoadjuvant chemotherapy treatment, with images and data showing physiological changes in the tumor in response to treatment. In the women who respond to therapy, the total hemoglobin concentration decreases and the level of oxygenation increases in the tumor over the course of the treatment. It is possible to predict a response to treatment as little as 4 days after the start of treatment. These findings demonstrate that optical techniques could play a role in the monitoring of changes in angiogenesis, apoptosis and hypoxia due to neoadjuvant chemotherapy.