The Mechanism of Action of Photodynamic Therapy

Abstract

Photodynamic therapy (PDT), one of the treatment modalities for cancer, uses a photosensitizer and laser irradiation to induce the production of reactive oxygen species in cancers cells. In Japan, the United States, and many other countries, PDT is widely used as a treatment option for solid cancers. In the therapeutic guidelines for lung cancer established in 2002 by the Japanese Ministry of Health, Labor and Welfare based on the principle of evidence-based medicine, PDT is the recommended treatment modality for centrally located early stage lung cancer. It has been reported that PDT rapidly induce apoptosis, inflammatory reaction, tumor specific and/or nonspecific immune reaction and damages the microvasculature of the tumor bed. The mechanism of action of PDT is unique and is not well known. In this paper, we discuss the mechanism of the induction of apoptosis or necrosis following PDT.