Abstract
In 1984 we developed laser hyperthermia (laserthermia), a system for transmitting low power Nd: YAG laser energy (2.0W) through an interstitial probe for local hyperthermia (43-44°C). Evaluating the effect of laserthermia, we histo-pathologically investigated the resected stomachs after preoperative pilot treatments on 20 patients with early gastric carcinoma. In 17 of 20 cases (85%) the bottom of the laserthermia induced ulcer showed no residual carcinoma, indicating the efficacy of treatment.
In 1986 photodynamic therapy (PDT) using a Q-switched Nd: YAG pulse laser and pheophorbide a (Ph-a) as a photosensitizer was developed. In vitro studies conducted after laser irradiation with and without Ph-a at 36.5°C±0.5°C for 15 min. showed survival rates of human colon adenocarcinoma of 27.2% and 65.3% respectively (control 89.7%). In vivo studies revealed that tumor bearing mice treated with Ph-a intraperitoneal injection and laser irradiation maintained a noticably elevated serum lipid peroxide level for at least one week, and that an 84% reduction in tumor size occured one wk. after irradiation. The results suggested that photo-chemical reaction occurred in cultured: carcinoma cells and tumor bearing mice, and lipid peroxide played an important role in PDT using an Nd: YAG pulse laser and ph-a.
