ABSTRACT
Photodynamic therapy (PDT) is a promising new therapeutic procedure for the management of a variety of solid tumors and many nonmalignant diseases. PDT is a two-step procedure that involves the administration of a photosensitizing agent, followed by activation of the drug with the nonthermal light of a speci c wavelength (Castano et al., 2004; 2005a,b). PDT generates singlet oxygen and other reactive oxygen species (ROS), which cause oxidative stress and membrane damage in the treated cells and consequently lead to cell death. e anticancer action of PDT is a consequence of a low-to-moderate selective degree of photosensitizer (PS) uptake by proliferative malignant cells, direct cytotoxicity, and a dramatic antivascular action that impairs the blood supply to the area of light exposure (Henderson and Dougherty, 1992). e PDT e ectiveness is determined by the oxygen supply and might be decreased in conditions causing tissue hypoxia (Busch, 2006). PDT as a treatment procedure has been accepted by the U.S. Food and Drug Administration for use in endobronchial and endo-esophageal treatment (Dougherty, 2002) and also as a treatment for premalignant and early malignant diseases of the skin (actinic keratoses), bladder, breast, stomach, and oral cavity (Dolmans et al., 2003).
