gms | German Medical Science

Objective: To evaluate the efficacy of interstitial radiosurgery (IRS) for pineal parenchymal tumors (PPTs).

Methods: 18 consecutive admitted patients (12 male and 6 female, age range 6–68 years, median age 34 years) with pineal parenchymal tumors (8 pineocytomas, 10 malignant PPTs) were treated at our institution with interstitial radiosurgery according to a prospective protocol using computer tomography (CT) and magnetic resonance imaging (MRI), and stereotactically guided iodine-125 seed implantation (¹²⁵I-IRS) as either primary or salvage therapy. The cumulative tumor surface dose ranged from 40-64 Gy. Adjuvant fractionated radiotherapy of the whole brain or the craniospinal axis was applied in patients with grade III and grade IV PPT. The median follow-up periods from the time of diagnosis and the time of IRS were 76.5 resp. 57.4 months.

Results: Overall 5- and 8-year survival rates after IRS were 100% and 86% for pineocytomas and 78% and 78% for high-grade PPTs. Follow-up MRI showed complete remission in 72.2% (13/18) and partial remission in 27.8% (5/18) of the cases. One patient developed an out-of-field relapse 4 years after partial remission of a pineocytoma, which was already treated with IRS. Three patients died during follow-up: one due to extracranial tumor spread, one due to suicide, and the third of unknown cause. There was no treatment-related mortality. Morbidity related to treatment was documented in one patient (5.6%).

Conclusions: This study shows that stereotactic ¹²⁵I-IRS for PPTs management is highly effective and safe. Because of its low rate of side effects, IRS may be an attractive alternative to microsurgery in de novo diagnosed pineocytomas. In malignant PPTs, IRS may be routinely applied in a multimodality treatment schedule supplementary to conventional irradiation.