Photodynamic therapy

Abstract

Photodynamic Therapy is a therapeutic modality that is based on the photodynamic reaction that occurs when photosensitive molecule is activated by a specific wavelenght light. During this reaction, oxigen active forms are created, that act at a cellular level, destroying cell membranes, cytoplasm and organelles leading to damage and cellular death. The administration of a photosensitizer agent intravenously leads to its absortion by all cells, but normal cells eliminate this agent in around 48 hours, while cancer cells retain it for a longer period of time (more than 48 hours). If photoactivation takes place in that period of time, it can produce tumor tissue destruction, that is quite specific afecting mainly tumoral cells. The destruction process is quite complex and not fully understood. We will discuss in this chapter the possible mechanisms of action and current indications and contraindications in lung cancer, advantages and limitations. Photodynamic therapy (PDT) is a minimally invasive modality used in the treatment of premalignant and malignant lung tumor. It’s a proven antitumor modality, well tolerated and with few negative effects. PDT uses photosensitizing substance called photosensitizer (PS) that accumulates selectively in tumor tissues leading to harmful reactive oxygen species formation and producing tissue death. In the last years, indications of lung cancer treatment have expanded, and PDT can be used as unique, neoadjuvant, or palliative therapy in the context of a multimodular treatment. It is minimally invasive; it can be applied as outpatient. PDT has many advantages: It is selective, damaging tumor tissue and sparing normal cells. It does not compromise additional of future treatments. It does not produce long-term side effects. It can be repeated many times. Low systemic toxicity. It is not mutagenic.