Basic Studies in Cancer PDT

Abstract

The first reports on photodynamic therapy (PDT) date back to the beginning of the last century, when researchers observed that a combination of light and certain chemicals could induce cell death. Significant efforts have been invested in the development of sensitizers to optimize the treatment since the photosensitizer is considered a critical element in PDT and should therefore at least meet some of the following criteria that are clinically relevant. Lots of sensitizers selectively localize within a tumor due to physiological differences in the tumor and healthy tissue; rather long-wavelength absorbing photosensitizers are preferentially used in oncologic PDT. The disadvantage of topical PDT in oncology is a limited penetration of the photosensitizer until few millimeters. Therefore mainly superficial tumors needing treatment up to 1 cm depth are amenable to PDT, with the exception being interstitial PDT or a combination of PDT with prior debulking surgery. In addition to the photodynamic therapeutic effect that occurs after light administration, photosensitizers can also be used diagnostically since many of these substances induce fluorescence. It is likely that PDT will continue to be used as both a solitary treatment modality and in combination with other strategies, such as hyperthermia and photodynamic therapy-generated vaccines.