[Evaluation of the efficacy of photodynamic therapy on experimental hepatocellular carcinoma--using local injection of photosensitizer].

The effect on photodynamic therapy (PDT) of using pheophorbide-a as a photosensitizer and Nd: YAG laser (Q-switch) was evaluated. Two hundred micrograms (0.1 ml) of pheophorbide-a was injected into tumors that had been subcutaneously implanted into the backs of nude mice (BALB/c-nu). Interstitial Nd: YAG laser irradiation (Q-switch; mean power 0.5 W, duration 10 min.) was performed 72 hours after pheophorbide-a injection. Forty-eight hours after laser irradiation, the areas of tumor necrosis were measured; these were larger in the group with the injection of pheophorbide-a than in those without. The areas of tumor necrosis after Nd: YAG laser irradiation at a higher mean power (Q-switch; mean power 2 W, control temperature 43-43.5 degrees C, duration 10 min.) were also measured. Again, the areas were larger in the group injected with pheophorbide-a. These results show that the injection of pheophorbide-a and interstitial irradiation using Nd: YAG laser induce a photodynamic reaction, and that this combination is useful in the treatment of deep-seated tumors.