Differences of photodamage in various malignant tissues which appear after application of photodynamic therapy using different laser systems

From 1989 to 1994 more than 600 various malignant foci were treated by more than 400 courses of PDT in the Lithuanian Oncology Center. During the application of PDT we used the following lasers: 35 MW He-Ne laser with 630-1 nm wavelength; 100-300 MW dye lasers with a wavelength of 629-3 nm, and a 100- 300 MW gold vapor laser, with a wavelength of 629-1 nm. We noticed some differences in results between the low-power lasers and the high-energy lasers. The initial response was better in patients whose tumors were irradiated with high-energy lasers, but the was more recidivism in this group. The most interesting thin we noticed was that there were significant differences in response of tumors of various histogenesis. for example, in most cases there was full necrosis of basal cell carcinoma immediately after PDT, but there were only some necrobiotical changes at the same time in other malignant tissues. Full necrosis in squamous cell cancer was noticed ont he third to fourth day after PDT. Full necrosis of malignant melanoma was noticed on the fifth to tenth day after PDT. It is important to emphasize that full melanoma necrosis was more frequently observed in cases where the low-power He-Ne laser was used for the PDT.