Treatment of a Large Acoustic Tumor with Fractionated Stereotactic Radiotherapy

Background: The treatment of acoustic neuromas (AN) usually involves surgical excision or stereotactic radiosurgery (SRS). However, for large AN (mean diameter >3 cm), SRS is rarely used, leaving patients with limited noninvasive treatment options. Recently, the use of fractionated stereotactic radiotherapy (FSRT) has been effective in treating small to medium-sized AN. We present a patient with large AN treated with FSRT. Methods: The patient was a 43-year-old man presenting with imbalance, tinnitus, vertigo, and right-sided hearing decline associated with vomiting and hydrocephalus. Magnetic resonance (MR) imaging revealed a large 3.8-cm right cerebellopontine angle tumor compressing the fourth ventricle. Following right frontal ventriculoperitoneal shunt placement, the patient underwent FSRT for treatment of the tumor. Using the Radionics X-Knife 4.0 3D treatment planning system, a total of 54 Gy was delivered in 1.8-Gy daily fractions with the prescription isodose line of 90%. Treatments were delivered using a dedicated Varian 6/100 linear accelerator, and head immobilization was achieved with the Gill-Thomas-Cosman relocatable stereotactic frame. The patient was subsequently evaluated with serial contrast-enhanced MR imaging. Results: Following FSRT, local control (defined as the absence of tumor progression) was achieved and treatment was well tolerated. There was no hearing-related, trigeminal or facial nerve morbidity following FSRT at the 63-month follow-up. Conclusion: Treating a patient with a large AN with FSRT resulted in local tumor control, with no trigeminal nerve, facial nerve or hearing-related morbidity. These results support FSRT as a potential noninvasive treatment modality for AN that some would consider too large for single-fraction SRS.