Standalone Gamma Knife Radiosurgery for Brain Metastasis of Malignant Peripheral Nerve Sheath Tumor

Abstract Background Brain metastasis (BM) of malignant peripheral nerve sheath tumor (MPNST) is extremely rare. The importance of aggressive surgical resection with or without radiation therapy has been emphasized, while the significance of other local therapies has been rarely reported. Three reports documented patients treated with stereotactic radiosurgery, while no previous study reported a BM case of MPNST treated with standalone Gamma Knife (Elekta AB, Stockholm, Sweden) radiosurgery (GKRS). The aim of this report is to describe the detailed clinical course of a patient with BM of MPNST and its radiographic response to standalone GKRS. Case Description The patient was a 29-year-old male with a history of MPNST. Seven years prior to the current presentation, he experienced respiratory symptoms, and a chest CT showed multiple pulmonary nodules. A bronchoscopic biopsy confirmed the diagnosis of metastatic MPNST. His disease was refractory to chemotherapy, and 1 month prior to this presentation, the chest and abdominal CT scans showed systemic progression. He developed worsening headache and left-side weakness. A brain MRI revealed a large right parietal (10.1 cm3) enhancing mass. Considering his poor general condition and the large size of the lesion, the tumor was treated with standalone GKRS. The 2-month follow-up MRI revealed the lesion was smaller and associated with surrounding ill-defined heterogeneous enhancements, compatible with asymptomatic radiation necrosis. This lesion showed a low cerebral blood volume, consistent with non-viable tumor. Unfortunately, the patient died from his primary disease before his second follow-up. Conclusions This is the first case report describing the details of the post-treatment course and radiographic responses following standalone GKRS in a patient with BMs from MPNST.