[Implantation of radioactive isotopes in intracranial tumors]

From may 1986 to July 1988 ten patients have been treated by interstitial implantation of radioactive isotopes using Yttrium 90 colloidal solution (9 cases) and Aurum 198 grains (1 case). There were 7 cystic out of 8 craniopharyngiomas, one malignant pituitary adenoma and one hemispheric Astrocytoma grade III-IV. In all but one patient the tumors were recurrent after one or more reductive or palliative operations. To external radiation undervent preoperatively two cases (one craniopharyngioma and one pituitary adenoma). Target volume was established by CT data and X-ray studies after stereotaxic injection of contrast medium (one case). Doses for intracystic irradiation were calculated using the Backlund's formula. The lowest activity was calculated to be 3.84 mCi, and the highest 12.9 mCi (m 6.8 mCi or 252 MBq). The delivered activity was 100-200 Gy of Y90 (m 140 Gy). The activity of Au198 was determined using the producers dosimetric tables. The radionuclide implantation was performed by stereotaxic techniques with Leksell's system in 5 patients. In 5 patients the surgical procedures were open: 3 osteoplastic supratentorial and 2 craniectomies for direct instillation of Y90 into the craniopharyngiomatous cavities spread to posterior fossa. Early short lasting side effects of endocavitary irradiation were observed in 5 patients (headache and somnolence; adynamy, pseudobulbar symptoms and rigor; insomnia and agressiveness; lack of orientation and increased mental irritability). The longest follow up was 26 months. The clinical response to intracystic instillation of Y90 was very favorable in 8 cases: 7 craniopharyngiomas and one pituitary adenoma. A satisfactory anatomical result with diminution or retraction of cystic cavities was evident in all cases. The more pronounced achievement of intracystic irradiation therapy in our series were the effects on stabilization or recuperation of vision and on improvement of visual field finding. The recovery of endocrine insufficiency was also noted. Two patients died: the 3-year old child, one year after implantation of Au198 grains in a huge calcified craniopharyngioma, and a woman, 67 old, twelve days after Y90 instillation to a hemispheric glioma grade III-IV.