Diffuse Optics in Treatment Monitoring for Photodynamic Therapy: Experience and Expectations
August 27th, 2019 THERESA M. BUSCH University of Pennsylvania

The cytotoxic action of photodynamic therapy (PDT) with many photosensitizers depends on the presence of molecular oxygen. Consequently, tumor physiologic properties such as oxygenation and blood flow can determine the efficacy of treatment. It is well established in animal models that PDT-induced changes in tumor oxygenation and blood flow will correlate with short and long-term treatment outcome. However, few have reported on clinical studies that investigate if physiologic properties of human tumors can associate with PDT outcome. Using diffuse optical technologies, we have investigated the association between lesion oxygenation and outcome in patients treated on a clinical trial of PDT for high-grade dysplasia, carcinoma-in-situ, or early microinvasive squamous cell carcinoma of the head and neck. Results suggest that measurement of the physiologic properties of previously unresected lesions may play a role in identifying patients with the highest probability of benefiting from PDT. In parallel with clinical investigations, we have undertaken preclinical studies to explore real-time, hemodynamic monitoring via diffuse correlation spectroscopy of PDT effect on tumor blood flow as a means to inform light delivery. Relative blood flow was measured in real-time during PDT, and through an automated feedback process, it was used to modulate irradiance so as to conserve tumor blood flow. Long-term tumor response (i.e., time-to-a-400 mm3 tumor volume) was significantly improved by blood-flow informed PDT; moreover, these improvements were not at the cost of lengthening the duration of treatment. Collectively, clinical and preclinical studies support efforts toward developing real-time personalized dosimetry that adjusts illumination parameters for PDT as a function of measured oxygenation and blood flow in the tumor microenvironment.

Seminar, August 27, 2019, 12:00. ICFO’s Seminar Room

Hosted by Prof. Turgut Durduran