Long-term results of upfront, single-session Gamma Knife radiosurgery for large cystic vestibular schwannomas.

Anecdotally, cystic vestibular schwannomas (cVSs) are regarded to have unpredictable biologic activity with poorer clinical results, and most studies showed a less favorable prognosis following surgery. While stereotactic radiosurgery (SRS) is a well-established therapeutic option for small- to medium-sized VSs, cVSs are often larger, thus making upfront SRS more complicated. The purpose of this retrospective study was to assess the efficacy and safety of upfront SRS for large cVSs. The authors reviewed the data of 54 patients who received upfront, single-session Gamma Knife radiosurgery (GKRS) with a diagnosis of large cVS (> 4 cm3). Patients with neurofibromatosis type 2, multiple VSs, or recurrent VSs and < 24 months of clinical and neuroimaging follow-up were excluded. Hearing loss (48.1%) was the primary presenting symptom. The majority of cVSs were Koos grade IV (66.7%), and the most prevalent cyst pattern was "mixed pattern of small and big cysts" (46.3%). The median time between diagnosis and GKRS was 12 months (range, 1-147 months). At GKRS, the median cVS volume was 6.95 cm3 (range, 4.1-22 cm3). The median marginal dose was 12 Gy (range, 10-12 Gy). The mean radiological and clinical follow-up periods were 62.2 ± 34.04 months (range, 24-169 months) and 94.9 ± 45.41 months (range, 24-175 months), respectively. At 2, 6, and 12 years, the tumor control rates were 100%, 95.7%, and 85.0%, respectively. Tumor shrinkage occurred in 92.6% of patients (n = 50), tumor volume remained stable in 5.6% of patients (n = 3), and tumor growth occurred in 1.9% of patients (n = 1). At a median follow-up of 53.5 months, the pre-GKRS tumor volume significantly decreased to 2.35 cm3 (p < 0.001). While Koos grade 3 patients had a greater possibility of attaining higher volume reduction, "multiple small thick-walled cyst pattern" and smaller tumor volumes decreased the likelihood of achieving higher volume reduction. Serviceable hearing (Gardner-Robertson Scale I-II) was present in 16.7% of patients prior to GKRS and it was preserved in all of these patients following GKRS. After GKRS, 1.9% of patients (n = 1) had new-onset trigeminal neuralgia. There was no new-onset facial palsy, hemifacial spasm, or hydrocephalus. Contrary to what was believed, our findings suggest that upfront GKRS seems to be a safe and effective treatment option for large cVSs.

Gamma knife radiosurgery for pituitary spindle cell oncocytomas.

OBJECTIVES: Spindle cell oncocytomas (SCOs) are benign lesions of the posterior portion of the pituitary gland that typically come to neurosurgical attention due to compression of the sellar or parasellar structures, and headaches. Initial treatment options for SCOs include surgical resection, particularly via the transsphenoidal approach. However, given that initial resection tends to be insufficient and subsequent revision surgery carries high complication risk, adjuvant treatment modalities may appear to offer promising solutions for controlling tumor progression. This report focuses on a potential new therapeutic option for SCOs, gamma knife radiosurgery (GKRS). PATIENTS AND METHODS: The authors identified all patients at one center who had a pituitary lesion treated with GKRS between 2005 and 2016. Five patients with histopathologically confirmed SCO who underwent GKRS were retrospectively identified and included in the present study RESULTS: The mean patient age was 52 years (range, 41-61 years). The most common presenting symptom was visual disturbance. All five patients had a history of transsphenoidal surgical resection prior to GKRS therapy. The mean tumor volume was 2.25 cm3 (range 0.7-5.38 cm3). The median tumor margin dose was 12 Gy (range, 12-14 Gy), and the median maximal dose was 24 Gy (range, 24-35 Gy). The median isodose was 50 (range, 40-50). No tumor volume progression was observed during radiological follow-up after GKRS (mean, 52 months; range, 36-84 months). At last follow-up, no neurological, endocrinological, or visual complications had been observed. CONCLUSION: Given their highly vascular and adherent nature, SCOs can be challenging tumors to treat, in particular when they recur. In our five cases, GKRS provided excellent tumor volume control for approximately 4.3 years on average. These results suggest that GKRS is a safe and effective treatment modality for histopathologically confirmed residual SCO.