Effect of hyperthermia on PDT and imaging

Photodynamic Therapy (PDT) is emerging as a successful tool to treat both malignant and benign tumors. It involves the interaction of a photosensitizer which upon activation by the appropriate light dose, leads to a cytotoxic and vasculotoxic photodynamic reaction. Improvements in PDT in areas such as the delivery and selectivity of photosensitizers, light-delivery and overall efficacy have helped to increase its attractiveness as an option for therapy. For optimizing the PDT treatment by a "see and treat approach," we have developed a number of tumor avid photosensitizers (PS) namely HPPH-Cyanine dye conjugates or other compounds (Iodinated photosensitizers) which have the ability for Optical and/or PET imaging as well as being effective photosensitizers for treatment. Hyperthermia refers to various techniques of heat application which may be delivered as a single modality or as part of an adjunct treatment option to the existing cancer therapies. Depending upon the temperature range used, hyperthermia might either directly induce cell kill or enhance the efficacy of other treatment modalities. Hyperthermia increases blood flow within the body, which may allow for higher dose delivery of photosensitizers with subsequent increased therapeutic efficacy of PDT. Hyperthermia could also increase the sensitivity of molecular imaging. The use of multifunctional photosensitizers for imaging and PDT is an emerging area and we have developed a few such agents in our lab. We wish to explore the use of hyperthermia to improve the use of such multifunctional photosensitizers from the point of view of imaging and/or therapy. Hyperthermia can be performed either as a whole-body mode or as localized mode. Our goal is to see which of the two heating modalities offers us better outcome.