Selective incorporation of 111In-labeled PHOTOFRIN by glioma tissue in vivo.

The use of PHOTOFRIN for photodynamic therapy of human gliomas has been studied by i.v. administration and laser photosensitization. Defining the uptake of PHOTOFRIN in the patient's tumor in comparison with the surrounding normal brain tissue is highly desirable for patient selection and study of in vivo kinetics. We utilized a non-invasive approach to the detection of PHOTOFRIN uptake in brain tumors with 111In-oxine radiolabeled PHOTOFRIN and external imaging and quantitation using a gamma camera. Biodistribution of 111In-labeled PHOTOFRIN in 13 organs was determined in four dogs and 15 mice with gliomas. 99mTc-DTPA was used as a control for nonspecific uptake. The greatest concentration of 111In-PHOTOFRIN in the brain tumor occurred at 24 hours post i.v. administration. The brain tumor PHOTOFRIN uptake was seven times greater than that of normal brain. The decreased blood background at 72 hours made this the optimum time for imaging. Specific tumor tissue uptake of 111In-PHOTOFRIN occurred, well beyond that resulting from blood-brain-barrier (BBB) breakdown.