The biodistribution of
boron sulfhydryl (BSH) was evaluated for
boron neutron capture therapy of
brain tumors. A selective
boron delivery to the
neoplasm is a prerequisite for successful therapy. The uptake of BSH after
intravenous administration was analyzed in neoplastic and normal tissues in 61 patients undergoing
craniotomies for intracranial
tumors. The patients received 10 to 100 mg of BSH/kg (5-50 mg of 10B/kg)
body weight, 2 to 72 hours before surgery. The
tumor boron concentrations ranged from 0.2 ppm (micrograms/g) in a low-grade
glioma to 19.5 ppm in a high-grade
glioma. The
tumor to blood
boron ratio rose above 1 in 15 of 24 high-grade intracerebral
tumors, 18 h or more after BSH infusion. The
boron concentration in high-grade
tumors was heterogeneous. Low-grade intracerebral
tumors showed a low
boron concentration with a
tumor to blood ratio below 1. Extracerebral
tumors, mainly
meningiomas, showed
boron concentrations comparable with high-grade
tumors, with a
tumor to blood ratio above 1 in 10 of 17 patients. The
boron concentrations in skin and muscle compared roughly with the blood values.
Boron did not enter normal brain in any significant amount. In high-grade
tumors,
tumor to brain ratios were above 2. Low
boron concentrations in normal brain make BSH safe for a Phase I normal tissue tolerance study. Computed tomographic contrast enhancement was evaluated to
tumor boron uptake for 30 patients.
Tumor enhancement on computed tomography does not permit the prediction of individual
tumor boron concentrations; however, the absence of a contrast enhancement was always associated with low
boron uptake.