The Treatment of a Large Acoustic Tumor With Fractionated Stereotactic Radiotherapy
Departments of 1Neurosurgery and 2Radiation Oncology, University of Minnesota Medical School, Minneapolis, MN
The treatment of acoustic neuromas (AN) usually involves surgical excision or stereotactic radiosurgery. However, for large AN (diameter > 3 cm), stereotactic radiosurgery 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.
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 3.77 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.
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 63-month follow-up.
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 acoustic neuromas some would consider too large for single-fraction stereotactic radiosurgery.
Fractionated Stereotactic Radiotherapy, Acoustic Neuroma, Tumor Size, Morbidity