Endoscopic photodynamic therapy in lung cancer

The main purpose of cancer therapy is to treat malignant tissue with the least damage to normal surrounding structures. Photodynamic therapy (PDT) seems to be able to fulfil this simple but fundamental premise. The mechanism of action of the photosensitizer- light system can be summarized in two main points. Chiefly, it seems to be a photodynamic process, with energy transfer from the light to the photosensitizer and from it to the oxygen molecules. Oxygen is excited and becomes singlet oxygen, which is extremely reactive and very noxious for tissues in which it develops. Secondly, a thermal mechanism related to light absorption and consequent temperature rise also seems to be involved in malignant necrosis by PDT. Thirteen males were submitted to endoscopic PDT. A total of 15 treatments were given: 2 patients were submitted to 2 sessions of PDT. Forty-eight hours after HPD administration (72 h in a few cases), the lesions were exposed to a 630 nm light from an argon-dye laser system. The total estimated energy dose delivered to the tumour surface was 90-150 J/cm 2 in 11 cases. All cases treated responded well and total disappearance was obtained. Median follow-up was 9.5 months (1-20 months) and the estimated energy delivered from 90-600 J/cm 2. No major complications were reported.