Microvascular effects of Photofrin(®)-induced photodynamic therapy

The 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.

The in vivo biological activities of Photofrin(®) exposed to the total laser energy density of 100J/cm(2) with the power density of 100 or 120mW/cm(2) at 630nm wavelength was studied. The amount of vascular damage produced in the chick chorioallantoic membrane (CAM) was evaluated. At 630nm wavelength, those individual vessels with a diameter of 40μm or less and those with a diameter between 40 and 100μm were treated with Photofrin(®) at a concentration of about 2.5mg/mL, and injected intraperitoneally at 2.5mg/kg, illuminated at 100 and 120mW/cm(2), respectively. Both exhibited coagulation.

There were no statistically significant differences between the two groups (100 and 120mW/cm(2)) 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 100mW/cm(2) treated group but not in the 120mW/cm(2) group. Statistically significant differences were also shown in arteriole and venules damage between 100 and 120mW/cm(2) 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 100mW/cm(2) treated group. There was no statistically significant difference in 120mW/cm(2) treated group.

Photofrin(®) 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.