Does photodynamic therapy have the necessary attributes to become a future treatment for organ‐confined prostate cancer?

present for a photodynamic effect to occur; photosensitizer, light and oxygen. The photosensitizer is administered in a stable form (ground state). It is then promoted to a higher energy state (singlet state) by light of a specific wavelength. The excited photosensitizer is then unstable and can release energy in one of three ways, i.e. emission of heat, emission of light, or conversion to an intermediate energy state (triplet state), before returning to stable ground state. In triplet state the photosensitizer can produce hydroxyl and superoxide radicals (type 1 reaction), or convert molecular tissue oxygen to form singlet oxygen (type 2 reaction). This singlet oxygen in turn reacts with proteins, lipids and nucleic acids in cells, causing functional and structural damage which leads to cell death. Hydroxyl and superoxide radicals are also directly responsible for cell death, although it is thought likely that type 2 reactions are more important for many of the photosensitizers [2]. It is likely that the immune response to PDT plays a part in its action, particularly in the long term. However, although this has been studied in animal models, it requires further study in the clinical setting [3].