PINEAL REGION TUMORS TREATED WITH INTERSTITIAL BRACHYTHERAPY WITH LOWACTIVITY SOURCES (192-IRIDIUM)

Three patients with tumours of the pineal region underwent interstitia l Ir-192 brachytherapy. Histological diagnoses were obtained in all pa tients, by stereotactic biopsy and included one germinoma, one mixed p ineoblastoma/pineocytoma, and one astrocytoma grade III. Our approach to pineal region neoplasms is first to decide whether sterotactic biop sy or surgery should be performed. When a pineal lesion is thought to be benign on the basis of imaging, such as benign teratoma, surgery is performed to resect the entire lesion. When a definitive diagnosis is not possible, stereotactic biopsy is performed to obtain a histologic al diagnosis for treatment planning, using a Brown-Roberts-Wells (BRW) stereotactic apparatus with computed tomography (CT) or magnetic reso nance imaging (MRI). When a lesion is malignant and localized, stereot actic implantation of catheters for interstitial brachytherapy is perf ormed simultaneously. Radioactive Ir-192 seeds are inserted into the c atheters and maintained for 5-10 days to give 36 Gy of irradiation at the tumour periphery. Sequential CT scans and MRI after treatment reve aled tumour disappearance in two patients with germinoma and high grad e astrocytoma and tumour reduction in the patient with mixed pineoblas toma/pineocytoma. No significant morbidity or mortality occurred in an y of these patients after stereotactic biopsy and brachytherapy. The t echnique and the advantages of this therapeutic approach to selected p ineal region rumours are described and discussed.