PHOTODYNAMIC THERAPY OF ORAL-CANCER - A REVIEW OF BASIC MECHANISMS AND CLINICAL-APPLICATIONS

Photodynamic therapy (PDT) is an experimental cancer treatment modalit y. PDT is based on the accumulation of a photosensitive dye in premali gnant and malignant lesions. A certain period of time after the dye ha s been administered, tumor tissue may contain more of the sensitizer t hen the surrounding normal tissues. When tissue containing the sensiti zer is exposed to light of a proper wavelength and dose, a photochemic al reaction between sensitizer and light will occur. The activated pho tosensitizer reacts with available oxygen which subsequently damages c ells and eventually may cause necrosis of the tumor. Photosensitizers can also be used for fluorescence detection. If a tumor contains more of the photosensitizer than the surrounding normal tissue, its fluores cence can potentially be utilized to detect tumors. Analogous to PDT, this can therefore be referred to as photodynamic detection (PDD). Thi s paper reviews the basic mechanisms and clinical applications of PDT and PDD, Emphasis is placed on PDD and PDT with the photosensitizer Ph otofrin for detection and treatment of premalignant epithelial lesions and squamous cell carcinomas of the oral mucosa.