Linac-Based Radiosurgery Treatment for a Pineal Parenchymal Tumor

Pineal parenchymal tumors (PPTs) are uncommon in general and rare in the adult population. Currently, the optimal treatment for PPT of intermediate differentiation (PPTID) in older patients is unknown. Stereotactic radiosurgery (SRS) has been used as both primary and adjuvant therapy, with single or fractionated doses using Gamma Knife (Elekta, Stockholm, Sweden) or CyberKnife (Accuray Inc., Madison, WI). This article presents the case of a 77-year-old woman with a biopsy-confirmed PPTID. She was treated with single fraction VMAT (volumetric modulated arc therapy)-based SRS on a Varian TrueBeam Edge linac (Varian Medical Systems, Palo Alto, CA) using multiple non-coplanar arcs. Contouring and treatment planning were performed on contrast-enhanced MRI and CT images. Accurate patient set-up and immobilization were achieved with an open-faced thermoplastic mask, real-time motion management using an optical surface monitoring system, and kV CBCT prior to each arc. The patient has shown excellent response for tumor size with frequent follow-up up to 84 months, but 25 months later developed double-vision and headaches with MRI revealing decreasing tumor size but enhancement and FLAIR changes in the adjacent brain parenchyma suggestive of radiation necrosis. These changes stabilized as of 32 months of follow-up, and then started to decrease by 35 months.