Monitoring Cancer Therapy with Diffuse Optical Methods

• Published in: Handbook of Photonics for Biomedical Engineering pp. 179 - 220
• Main Authors: Sunar, Ulas, Rohrbach, Daniel J.
• Format: Book Chapter
• Language: English
• Published: Dordrecht Springer Netherlands
• Subjects: Blood flow; Cancer therapy; Diffuse correlation spectroscopy; Diffuse optical imaging; Diffuse optical spectroscopy; Diffuse reflectance spectroscopy; Monitoring and predicting response; Oxygen metabolism; Oxygenation
• ISBN: 9789400750517; 940075051X
• DOI: 10.1007/978-94-007-5052-4_26

This review focuses on noninvasive monitoring of the therapeutic responses of tumors via assessment of tumor vascular and hemodynamic parameters. The diffuse optical techniques provide a promising means for noninvasive imaging of deep tissues. During the last few years, researchers have focused on developing diffuse optical techniques to provide complementary information with multiple parameters. These techniques permit real-time, noninvasive quantification of tissue hemoglobin concentration, blood oxygen saturation, blood flow, and drug concentration in vivo. Multiparameter approach increases sensitivity and specificity along with providing a more complete picture of physiological mechanisms and ultimately prediction of the response. The instrumentation is portable and rapid, and it has enabled the study of tissue responses in a variety of settings of monitoring cancer treatments in preclinical and clinical settings. After presenting the niche for the diffuse optical methods in the Introduction section, the basic principles of photon propagation in tissue will be provided in section “Theoretical Background.” After several instrumentation, examples will be presented in section “Instruments,” preclinical applications will be provided in section “Preclinical Applications.” In preclinical cases, examples of antivascular therapy and photodynamic therapy (PDT) in small animals will be provided. The effects of an antivascular drug, combretastatin, were monitored continuously and were found to induce substantial reduction of blood flow and tissue oxygen. The observations of blood flow and oxygenation were then correlated with power Doppler ultrasound and hypoxia biomarker techniques, respectively. Then PDT fluence rate effects on skin and head and neck cancer models for superficial and deep tissue imaging are provided. As clinical applications in section “Clinical Applications,” PDT and chemoradiation monitoring in patients with head and neck cancer and chemotherapy monitoring in breast cancer patients will be presented. Pilot studies revealed that early changes in diffuse optical parameters correlate well with the end-point clinical responses. Total hemoglobin concentration, blood oxygen saturation, blood flow, and drug consumption during treatment showed variable sensitivity to the therapy for different individuals, thus emphasizing the need for simultaneous monitoring of multiple tissue parameters for individualized treatment planning.