SELECTIVE INCORPORATION OF IN-111-LABELED PHOTOFRIN(TM) BY GLIOMA TISSUE IN-VIVO

The use of PHOTOFRIN(TM) for photodynamic therapy of human gliomas has been studied by i.v. administration and laser photosensitization. Def ining the uptake of PHOTOFRIN(TM) in the patient's tumor in comparison with the surrounding normal brain tissue is highly desirable for pati ent selection and study of in vivo kinetics. We utilized a non-invasiv e approach to the detection of PHOTOFRIN(TM) uptake in brain tumors wi th In-111-oxine radiolabeled PHOTOFRIN(TM) and external imaging and qu antitation using a gamma camera. Biodistribution of In-111-labeled PHO TOFRIN(TM) in 13 organs was determined in four dogs and 15 mice with g liomas. Tc-99m-DTPA was used as a control for nonspecific uptake. The greatest concentration of In-111-PHOTOFRIN(TM) in the brain tumor occu rred at 24 hours post i.v. administration. The brain tumor PHOTOFRIN(T M) uptake was seven times greater than that of normal brain. The decre ased blood background at 72 hours made this the optimum time for imagi ng. Specific tumor tissue uptake of In-111-PHOTOFRIN(TM) occurred, wel l beyond that resulting from blood-brain-barrier (BBB) breakdown.