Phosphorus-32 therapy of cystic Grade IV astrocytomas: Technique and preliminary application

Instillation of [³²P]chromic phosphate to cystic brain tumors was performed in six patients. Three patients had craniopharyngioma, two had Grade IV astrocytoma and one had Grade II astrocytoma. The cyst volumes ranged from 2 to 44 cc. A calculated dose of 20,000 rad was delivered to the cyst wall. The [³²P]chromic phosphate dose given to achieve this dose ranged from 0.11 mCi to 2.5 mCi. Radionuclide leakage was not detected in either the central nervous system or the reticuloendothelial system by bremsstrahlung scanning. Stereotactic instillation was done in some cases, others had indwelling catheters. The frequency of cyst fluid aspiration in the three patients with craniopharyngioma decreased postinstillation. In the two patients with Grade IV astrocytoma, reductions in both the CT documented cyst size as well as the frequency of cyst aspiration were noted. We conclude that [³²P]chromic phosphate instillation by stereotactic or indwelling catheter method is a safe and helpful procedure in the management of cystic brain tumors.