[Photodynamic therapy in the early treatment of cancer]

The clinical application of photodynamic therapy (PDT) began in the late 1970's. Hematoporphyrin derivative has been used as a photosensitizer and recently Photofrin II (Dihematoporphyrin ether, DHE) was also developed as a second generation photosensitizer. The argon dye laseris used to excite the photosensitizer, however an eximer dye laser was recently developed as more effective laser. In a multicenter research study project team (7 institutions) on photodynamic therapy organized by the Ministry of Health and Welfare, 133 cases of gastric cancer (including 120 cases of early stage cancer), 209 cases of lung cancer (69 cases of early stage cancer), 66 cases of esophageal cancer (22 cases of early stage cancer), 68 cases of bladder cancer (68 cases of early stage cancer), and 86 cases of other organ cancers were treated. In early stage cancer cases 77.3% showed complete remission (CR) but among those the recurrence was 15.7% in lung cancer cases and opposed to 100% CR and 22.2% recurrence in gastric cancer cases, 80% CR and no recurrence in esophageal cancer cases, and 68.6% CR and 58.3% recurrence in bladder cancer cases. Especially in limited lesions less than 1 cm in diameter, the CR was obtained in 100% and the recurrence was recognized in only 1 (2.6%) of 28 lung cancer lesions, 100% CR and no recurrence was obtained in 30 lesions of gastric cancer and also 100% CR with no recurrence was recognized in 16 lesions in bladder cancer. This study suggests that PDT has the potential to cure early stage cancer lesions.