Microvascular effects of Photofrin®-induced photodynamic therapy

SummaryBackground and objectiveThe object of our study is to evaluate the feasibility of photodynamic therapy (PDT) for complicated hemangiomas. The photosensitizing activities of Photofrin® have been used in vivo models for our goal of evaluation.Study design/materials and methodsThe in vivo biological activities of Photofrin® exposed to the total laser energy density of 100 J/cm2 with the power density of 100 or 120 mW/cm2 at 630 nm wavelength was studied. The amount of vascular damage produced in the chick chorioallantoic membrane (CAM) was evaluated. At 630 nm wavelength, those individual vessels with a diameter of 40 μm or less and those with a diameter between 40 and 100 μm were treated with Photofrin® at a concentration of about 2.5 mg/mL, and injected intraperitoneally at 2.5 mg/kg, illuminated at 100 and 120 mW/cm2, respectively. Both exhibited coagulation.ResultsThere were no statistically significant differences between the two groups (100 and 120 mW/cm2) on vessel damage grade 1. With vessel damage grades 2 and 3, the differences were statistically significant between two groups. Vessel damages between arterioles and venules also demonstrated differences in the 100 mW/cm2 treated group but not in the 120 mW/cm2 group. Statistically significant differences were also shown in arteriole and venules damage between 100 and 120 mW/cm2 treated groups. The severity of vessel damage between grades 1 and 2, 1 and 3, and 2 and 3, were compared. The differences were statistically significant in 100 mW/cm2 treated group. There was no statistically significant difference in 120 mW/cm2 treated group.ConclusionPhotofrin® has the capabilities for destruction of microvascular vessels of CAM. Extension of this study to the second-generation photosensitizers is underway. The most important treatment variables seem to be the power density.