ABSTRACT
Due to the high reactivity and short half-life of the ROS, only cells that are proximal to the area of the ROS production (areas of photosensitizer localization) are directly aected by PDT [25]. Hence, small-diameter optical bers may be placed interstitially to deliver PDT light to either a portion of the prostate or the entire gland, using a variety of imaging techniques to achieve accurate positioning [26,27]. PDT may spare a suf-cient amount of the neurovascular bundle so that sexual potency is preserved. Another advantage compared with other modalities where salvage therapy is limited is the ability to treat locally recurrent prostate cancer aer prior radiation therapy [1,4,5,18], and PDT itself can be repeated several times if necessary. However, the PDT ecacy and the extent of photodamage and cytotoxicity is multifactorial, depending on the type of sensitizer, its extracellular and intracellular concentration and localization that depend also on the drug-light time interval, the total light dose delivered and local light uence rate (ϕ), and the availability of molecular oxygen [1,2,4,9,12-18,25]. All of these factors are interdependent and may change dynamically during treatment.
