CHAPTER 22: Contrast-Enhanced Imaging of Photodynamic Therapy in Pancreatic Cancer: From Mouse to Man

Studying the effects of photodynamic therapy (PDT) in pancreatic cancer is challenging as it involves understanding the complex interplay of photosensitizer, light delivery and tissue oxygenation in tumors, which are well known to be heterogeneous and hypo-vascularized relative to the normal pancreas. In order to better illuminate the parameter space of what factors dominate the treatment response, imaging studies have been carried out using several contrast-enhanced imaging methods (magnetic resonance imaging, computed tomography [CT] and optical) and have been applied to imaging both the pre-treatment parameters and the post-treatment outcomes. Preclinical models in mice and rabbits have been extensively used and a phase I human clinical trial has been completed, called VERTPAC-1. The preclinical contrast imaging studies suggested that vascular-based photosensitizer delivery would dominate PDT efficacy, and that delivery of verteporfin is well predicted by tissue perfusion. However, post-analysis of the VERTPAC-1 data showed that contrast CT-enhancing blood volume was inversely correlated to treatment outcome of the volume of necrosis, as assessed by post-treatment contrast CT. Taken together, these data illustrate how an interpretive approach to dosimetry can be done with contrast imaging examinations.