Diffuse optical spectroscopic imaging measures tumor functional response to bevacizumab: initial studies.

Abstract

Abstract Abstract #6056 Background: Diffuse Optical Spectroscopic Imaging (DOSI) is a non-invasive, bedside functional imaging technique that quantifies the concentrations and molecular states of tissue hemoglobin, water, and lipids. Pilot studies have shown that DOSI may be a useful tool for quantifying neoadjuvant chemotherapy response, typically by comparing the degree of change in tumor water and deoxy-hemoglobin concentrations before and after therapy. DOSI may offer a point-of-care measurement of tumor responses to therapeutic intervention. The majority of these DOSI studies have measured responses to Anthracyclines. However, the optical response to Bevacizumab has not been demonstrated in vivo in human subjects.
 Materials and Methods: Twenty-one patients diagnosed with stage II/III cancers were followed with DOSI prior to and during their two-stage neoadjuvant chemotherapy regimen that featured (a) Anthracyclines (2-4 cycles) and (b) Trastuzumab/Bevacizumab (for HER2+/HER2- status, respectively). Changes between pre-treatment and pre-surgical DOSI-measured parameters were compared against final surgical pathology (complete, partial, or non-responder). A functional tissue optical index (TOI) was calculated that has been shown to discriminate between normal and malignant tissues.
 Results: Both short-term and long-term changes in tumor physiology were observed. For both therapy strategies (N=21), statistically significant changes were measured in TOI from baseline to pre-surgery between complete (95+/-15%), partial (79+/-11%) and non-responders (38+/-42%). TOI changes after the initial therapy stage were strongest in patients with more favorable pathological responses (78%, 56%, and 12% for complete, partial, and non-responders respectively). For patients receiving Bevacizumab (N=9), more detailed serial image analysis of tumor deoxy-hemoglobin revealed short-term changes (7-14 days) where initial decreases in hemoglobin were soon followed by slow increases back to pre-treatment levels. Two of the patients who received Bevacizumab demonstrated detectible residual disease by DOSI after completion of all neoadjuvant therapy, despite that contrast-enhanced MRI signals had disappeared.
 Discussion: We have provided evidence that DOSI may be well-suited to monitor the response of different cancer drugs, including anti-angiogenic compounds such as Bevacizumab, in breast cancer patients. While the usage of Bevacizumab in human subjects is still under investigation in breast cancer, we foresee that DOSI may be a useful tool in general for the development of drugs and dosing strategies. Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 6056.