Mechanisms of photodynamic therapy

Photodynamic therapy (PDT) is an established photochemical treatment. PDT uses photosensitizer (PSs) that are excited by light at a particular wavelength after being stimulated by light; reaction with molecular oxygen creates reactive oxygen species in target tissues, causing cell death. Compared to conventional treatment methods, conventional therapy methods are more effective. The advantages of PDT over other conventional cancer therapies are its low systemic toxicity and the ability to selectively destroy light-accessible tumors. It is based on the activation of the photochemical properties of substances called PSs, resulting in cellular or vascular damage. The PDT has greater selectivity over tumor cells due to the use of preferably localized PSs in tumor lesions and the accurate light radiation of these lesions. PDT is not a systemic treatment, but a local treatment and is only suitable for localized diseases. This book chapter summarizes the mechanisms of PDT action and how they can be manipulated to improve the clinical outcome in patients.