Some Aspects for Improving Photodynamic Therapy

Abstract

Photodynamic therapy (PDT) is a minimal invasive treatment to deal with common oncologic diseases as an alternative to other strategies. In the PDT treatment, three elements are essential: light, a photosensitizer and oxygen. The photosensitizer achieves a larger concentration in the neoplastic tissue than in the normal one, and the photodynamic reaction generates highly reactive species that destroy the malignant tissue. The light wavelength for illuminating the tissue is usually chosen in the 390 – 800 nm range, where most of the photosensitizers exhibit absorption peaks. Furthermore, the photosensitizers and their derivatives show a large fluorescence that can be used to detect the extension of the neoplastic tissue for better planning of the treatment strategy. Firstly, some basic concepts about the photodynamic diagnosis and treatment of neoplastic diseases are given. Then some important considerations to improve PDT outcome are pointed out, based on experiments from our group and other authors employing different light sources and application protocols. Finally, some comments on clinical applications are given. The PDT appears to exhibit many advantages in comparison to other treatment modalities that can potentiate the choice of this treatment strategy.