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Selective ablation of rat brain tumors by boron neutron capture therapy
J Coderre1, P Rubin, A Freedman
1Medical Department, Brookhaven National Laboratory, Upton, NY 11973.
Purpose:
Damage to the surrounding normal brain tissue limits the amount of radiation that can be delivered to intracranial tumors. Boron neutron capture therapy (BNCT) is a binary treatment that allows selective tumor irradiation. This study evaluates the damage imparted to the normal brain during BNCT or x-irradiation.
Methods And Materials:
The brains of rats with implanted 9L gliosarcomas were examined 1 year after tumor-curative doses of either 250 kV X rays or BNCT. Histopathologic techniques included hematoxylin and eosin staining, horseradish peroxidase perfusion, and electron microscopy.
Results:
Longterm X ray survivors showed extensive cortical atrophy, loss of neurons, and widespread leakage of the blood-brain barrier (BBB), particularly around the tumor scar. In contrast, the brains and the BBB of longterm BNCT survivors appeared relatively normal under both light- and electron-microscopic examination. Intact blood vessels were observed running directly through the avascular, collagenous tumor scar.
Conclusion:
The selective therapeutic effect of BNCT is evident in comparison to x-irradiation. Both groups of animals showed no evidence of residual tumor at 1 year. However, with x-irradiation there is no therapeutic ratio and tumor eradication severely injures the remaining brain parenchyma. These observations indicate a substantial therapeutic gain for BNCT.