Hematoporphyrin derivative photoradiation therapy of the rat 9L gliosarcoma brain tumor model

The distribution of hematoporphyrin derivative (HPD) in the rat 9L gliosarcoma intracerebral brain tumor model at 4, 24, 48, and 72 hours after intravenous administration was evaluated using a digital video fluorescence microscopy technique. Maximum tissue fluorescence in the normal brain was observed at 4 hours, whereas maximum fluorescence in the tumor regions occurred at 24 hours. Although the fluorescence counts suggested that there was significant uptake of HPD within the tumors when compared to normal brain, only 33% to 44% of each of the eight tumors surveyed showed fluorescence. In response to a laser light dose (633 nm) of 30 J/cm2, six rats that had been sensitized with HPD had a patchy coagulation necrosis involving up to 70% of the total tumor volume. In contrast, four rats given HPD only or exposed to laser only had no areas of necrosis, as observed on histological examination. In a group of 30 rats, no prolongation of survival was observed in response to photoradiation therapy.