Dynamic tomographic optical breast imaging (TOBI) to monitor response to neoadjuvant therapy in breast cancer.

Background: Near-infrared optical measurements have been recently shown to offer a promising non-invasive way for monitoring breast neoadjuvant chemotherapy (NAC) and predicting outcome. In particular, snapshots of tissue oxy and deoxy-hemoglobin concentration as well as water and lipid content have been demonstrated to be sensitive to therapy-induced changes. In this study, we extend optical measurements to capture additional hemodynamic and metabolic biomarkers revealed by dynamically imaging breast tissue during fractional mammographic compression. Using our dynamic tomographic optical breast imaging (TOBI) system we evaluate the early prediction performance of this advanced technology. Methods: We are conducting a pilot feasibility study in female patients with unilateral locally advanced breast cancer undergoing standard-of-care NAC. Pre-treatment and day 7 post-treatment TOBI scans are obtained, with additional (optional) scans on day 1 of each subsequent chemotherapy cycle. Both breasts are compressed in turn to 4-8 lbs of force, and optical images are acquired once every 2 seconds over two minutes. Time-resolved oxy-(HbO), deoxy-(HbR), and total-(HbT) hemoglobin concentration and hemoglobin oxygen saturation (SO2) are calculated. The compression-induced rate of change of HbT correlates with changes in tissue blood volume indicative of biomechanical properties. The evolution of tissue SO2 is modeled to obtain an index of the ratio of oxygen metabolism to blood flow. Therapy induced changes are quantified, and comparisons between changes in responders vs. non-responders are performed (response is defined here as >50% reduction in the largest tumor diameter). Results: We have enrolled 20 patients so far, of which 90% (N = 18) completed both the day 0 and day 7 scans. 17 patients have undergone surgery at this point. We focused our initial analysis on 5 HER2+ patients, of which two were non-responders, and three were responders according to our criteria. Four patients received taxol+herceptin+lapatinib, while the other received taxol+lapatinib only. In this small subgroup, the non-responders had an average increase of 1% in total hemoglobin concentration (HbT) from day 0 to day 7, while the responders had an average 12% decrease in HbT, respectively. We also noted different trends in the evolution of the tissue oxygen consumption to blood flow ratio, which increased 32% in non-responders from day 0 to day 7, while decreasing 11% in responders. Conclusions: The large percentage of enrolled patients that completed both initial scans demonstrates the feasibility of using dynamic optical breast tomography for breast neoadjuvant chemotherapy monitoring. Results in a small cohort of 5 HER2+ patients suggested a decreasing trend in HbT for responders as observed by previous studies. We also report for the first time an increase in the metabolic ratio of oxygen consumption to blood flow in non-responders vs. a decrease in responders. These initial results of our on- going study suggest that dynamic TOBI can detect changes due to treatment and may have predictive value for the treatment outcome and supports further studies of this non- invasive and portable tool for chemotherapy monitoring. [ABSTRACT FROM AUTHOR]