PDT — State of the Art

Photodynamic therapy is an experimental treatment for solid tumors. Photodynamic therapy (PDT) consists of the activation of a photosensitizing agent by light. This photodynamic reaction produces damage to the tissue containing the photosensitizer and exposed to light and in presence of oxygen. The idea of treating tumors by photosensitizers is as old as the early ’900; already in the 1903 topic application of eosin and esposition to sunlight was known to produce response by skin tumors (1). On the other hand Policard, 1924, observed reddish fluorescence in animal and human tumors observed under Wood lamp. The presence of fluorescence was attributed to endogenous porphyrins accumulated after infection of the observed tissue by hemolytic bacteria (2). In 1942 Auler and Banzer (3) reported animal tumor fluorescence after systemic administration of Hematoporphyrin (HP) and in 1960 Lipson and coworkers prepared the Hematoporphyrine derivative (HPD), a mixture of porphyrins obtained treating HP with acetic and sulphuric acids (4). They demonstrated that HPD was selectively accumulated by malignant as well as by actively proliferating tissues and realized the first demonstration of endoscopic diagnosis of malignant tissues by detection of fluorescence in the respiratory and in the upper digestive tract (5). After the development of laser, fluorescence diagnosis and particularly PDT have been furtherly studied and the advantage of laser on filtered lamp light has been demonstrated by the possibility of obtaining the necessary power of light with a very narrow band (630 nm wavelength).