FLUORESCENCE LOCALIZATION IN TUMOR AND NORMAL BRAIN AFTER INTRATUMORAL INJECTION OF HEMATOPORPHYRIN DERIVATIVE INTO RAT-BRAIN TUMOR

In the intracerebral 9L rat gliosarcoma, the spatial distribution of t he photosensitizer haematoporphyrin derivative (HPD) was studied after intratumoral injection. The fluorescence volume was measured in histo logical sections from 10 min up to 5 days after injection. Complete se nsitization of the tumours could not be achieved by slow stereotactica l injection of 4 mm(3) HpD (mean HpD fluorescence volume, 13+/-11 mm(3 )). Larger parts of the tumour could be loaded with HpD (39+/-23 mm(3) , p=0.0001) by increasing the injection velocity and the volume to 50 mm(3). Again, complete sensitization of the tumours was not achieved d uring a time scale of 5 days after intratumoral injection. Although th e fluorescence volume did not change significantly with time, it was i nfluenced by the injection site within the tumour. Injection of HpD wi thin 1 mm from the tumour border resulted in significantly smaller flu orescence volumes in the tumour than injection into the tumour centre. Large injection volumes caused an increased leakage of HpD to normal brain, leading to the loss of selectivity of photosensitizer content a nd the occurrence of dark toxicity of normal brain while the tumours s till appeared vital.