Three-Fraction Stereotactic Radiosurgery for Treatment of Vestibular Schwannoma (Acoustic Neuroma) in Patients with Neurofibromatosis Type 2

Abstract

Neurofibromatosis type 2 (NF2) patients risk complete deafness from either bilateral vestibular schwannoma (VS) or its treatment. Both microsurgical resection and Stereotactic radiosurgery (SRS) have been associated with poorer rates of hearing preservation in patients with NF2 than in sporadic VS. In an attempt to maximize hearing preservation while maintaining good tumor control, we have conducted a prospective trial of three fraction SRS for the treatment of VS in patients with NF2. Eleven VS in 10 patients with NF2 were treated. Conventional frame-based Stereotactic localization was used. Mean maximal tumor diameter was 19.5 mm (range 11–28). A total dose of 21 Gy was administered in 7 Gy fractions with a mean interfraction interval of 12 hours. Patients were evaluated with neurologic examination, MRI, and audiometry. No patients were lost to follow-up. One patient died due to complications following surgical resection of a contralateral VS. Tumor (10–46 months posttreatment, mean 26 months) was stable or decreased in 9 of 10 tumors (90%). One patient experienced slight tumor enlargement at 27 months, which subsequently regressed. Actuarial rate of hearing preservation at 2 years was 67%. All patients (n = 5) with good pretreatment hearing (Gardner–Robertson grade 1 or 2) had preserved useful hearing (grade 1–3) at 1 year. Two patients (grade 3 and 4 hearing) lost all hearing within 24 hours of treatment; another patient with grade 3 hearing lost residual hearing over 6 months. One patient developed facial spasms. Three-fraction SRS for acoustic neuroma is well tolerated in patients with NF2 and is associated with a lower risk of hearing loss and other cranial neuropathy than single-fraction treatment. Continued follow-up will be necessary to evaluate long-term tumor control and hearing preservation.