Photodynamic therapy--mechanism and employment.

Photodynamic terapy (PDT) is a new treatment for a wide variety of malignancies and premalignant dysplasias, as well as some non-cancer indications. Therapeutic response to PTD is achieved through the activation of non-toxic photosensitiser located within neoplastic tissue, using visible light tuned to the appropriate absorption band of the photosensitiser molecule. This produces cytotoxic free radical such as singlet oxigen, which result in local photo-oxidation, cell damage and destruction of the tumour cells. Systemic administration of photosensitisers has been used with endoscopic light exposure to treat a variety of internal malignances. A topical drug delivery is used in the skin deseases treatment. The selective distribution of photosensitiser in the target tissue is the fundamental to the process of PDT. This tissue specific photosensitation and normal tissue sparing results in good healing and often very good cosmetic results. Peterson PTD can be used for the treatment of cutaneous lesions (e.g., SCC, BCC, Bowen's disease, mycosis fungoides, erythroplasia of Queyrat, Gorlin's Syndrome, actinic keratoses), lower genital tract neoplasia (VIN and CIN), gastrointestinal tumours, etc., as well as nononcological indications (e.g., acne, condyloma acuminatum, lichen planus, psoriasis, vitiligo, vulval lichen sclerosus, warts and verrucae).