Abstract P4-03-04: Dynamic tomographic optical breast imaging (TOBI) for neoadjuvant chemotherapy monitoring

Abstract

Abstract Background: Dynamic Diffuse optical imaging using near-infrared light was shown to be promising method for neoadjuvant therapy monitoring as an alternative functional imaging that is low-cost, non-invasive, portable, safe and simple to operate. While optical breast imaging methods rely on "static" assessments of tissue oxy- and deoxy- hemoglobin concentration without contrast agents, they are insufficient for clinical applications. Dynamic tomographic optical imaging induces tumor-sensitive hemodynamic variations, as a contrast mechanism, driven by fractional mammographic compression. These tumor contrast measurements are governed by interlay of tissue biomechanics and oxygen metabolism. In this study we seek to evaluate the predictive value of these biomarkers with respect to treatment outcome. Methods: A group of 22 patients with locally advanced breast cancer were scanned using our dynamic TOBI system before and during neoadjuvant chemotherapy. In this analysis we focused on pre-treatment, day 7 and day 30 post-treatment dynamic TOBI scans. Both breasts are compressed in turn to 4-8 lbs of force (depending on size) and optical images are acquired every 2 seconds over 2 minutes. We calculate the time course of oxy (HbO), deoxy (HbR)and total (HbT) hemoglobin concentration as well as the hemoglobin oxygen saturation (SO2). Regions of interest are defined in the optical images to correspond to the radiology identified tumor location, and the healthy tissue in the same breast, respectively. We compare the time courses in the two regions at baseline, day 7 and 30 days after initiation of treatment. Results: In this analysis we present results from 10 patients including 6 responders (defined as greater than 50% reduction in the largest tumor axis from baseline imaging and final pathology) and 4 non-responders. As the compression plates are held in place the tissue collagen matrix begins to stretch, effectively reducing the compression force. At baseline, all patients exhibit a decrease followed by delayed recovery in HbT, and SO2 in the tumor area, in contrast to immediate recovery in surrounding tissue. At day 7 and 30, this contrast is maintained in non-responders (<50% reduction in tumor maximum diameter); however, in responders, the contrast starts decreasing at day 7 and substantially disappears at day 30. Average changes in HbT and SO2, show that the contrast between normal and tumor increases somewhat at day 7 and more noticeably at day 30 in non-responders to NACT. Comparing hemodynamic changes in responders and non-responders, it is clear that at three selected time points (30, 60 and 90 s) during the scan, the contrast between tumor and normal tissue in both ΔHbT and ΔSO2 is reduced for the responders at day 7 and day 30. Conclusions: These initial results suggest that dynamic optical breast imaging can detect changes due to treatment and have predictive value for the treatment outcome. DTOBI can show the difference in hemodynamic response to compression between tumor and normal tissue and demonstrates the feasibility of using dynamic optical breast tomography for neoadjuvant chemotherapy monitoring. ongoing. Citation Format: Sajjadi AY, Singh B, Deng B, Boas DA, Moy B, Schapira L, Bardia A, Specht MC, Carp SA, Isakoff SJ. Dynamic tomographic optical breast imaging (TOBI) for neoadjuvant chemotherapy monitoring. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P4-03-04.