Photodynamic laser therapy in tracheo bronchial endoscopy

Hp and HpD have been found to be accumulated and retained by tumor tissues; intravenous Hp or HpD disseminates throughout the entire body, but it rapidly clears out of the normal cells, while remaining longer in tumor tissue, where it is 5-6 times more concentrated after 48-72 hours. Photo-Dynamic Therapy is based upon specific photosensitization of malignant tissue containing Hp after exposure to a visible activating light in the red region of the spectrum (630 nm). Absorption in the red allows deep penetration into tissue, biological effects of using this wavelength are in the order of 5-15 mm of tumor tissue thickness. Photosensitization produces a photochemical reaction releasing singlet Oxygen, that causes tissue death. The singlet Oxygen damages some biological processes such as replay and repair of nucleic acids, cell respiration, protein synthesis and cell membrane function. How-ever, the tissue damage is caused by involvement of the tumor microvascular system too. Many authors report that effects of PDT are secondary to the destruction of tumor microvasculature and the first observable signs occur in the subendothelial zone of the tumor capillary wall. PDT is effective in tracheobronchial endoscopy in treatment of precancerous lesions and early stage lung cancer. PDT has been employed in treatment of advanced carcinoma associated with YAG-Laser and Radiotherapy. (author). 29 refs., 1 tab