Carbohydrates as potential diagnostic tracers for brain tumors

Currently available diagnostic tracers for brain tumors are not specific. Tumor-specific tracers would improve the detection of brain tumors by gamma encephalography. Glucose is an important substrate for tumor metabolism and is known to be taken up in large amounts. The authors have studied five labeled carbohydrates in an attempt to find a tumor-specific tracer: three were tritiated (L-galactose-1-3H, L-fucose-3H, and 4,6-dideoxy-xylo-hexose-3H) and two were radioiodinated (methyl-6-125I-6-deoxy-D-glucoside and 6-125I-6-deoxy-D-glucose). The uptake of these tracers by a transplantable mouse ependymoblastoma after intravenous injection was determined by liquid and well scintillation counting. The highest tumor-to-brain ratio was 7.1 to 1 for the tritiated tracers and 6.2 to 1 for the radioiodinated tracers. Although these ratios are not high enough for gamma encephalography, one of the iodinated tracers may be useful for enhancement of contrast in computerized axial tomography.