Fractionated stereotactic radiotherapy (FSRT) is a noninvasive treatment for acoustic neuromas (ANs). Initial reports from our institution demonstrated that the reduction of treatment dose to 46.8 Gy resulted in improved preservation of functional hearing status.

We now report the tumor control (TC), symptomatic outcome, and hearing preservation (HP) rate in patients treated with reduced-dose FSRT.

We analyzed all patients with AN treated from 2002 to 2011. All patients received 46.8 Gy in 1.8-Gy fractions. Follow-up audiogram and magnetic resonance imaging were performed in ≤ 1-year intervals. TC and HP were calculated by the Kaplan-Meier method. Analysis of HP, defined as Gardner-Robertson value ≤ 2, was determined by audiometric data. Non-hearing-related symptoms were defined by Common Terminology Criteria for Adverse Events version 4.

In total, 154 patients were analyzed. At a median follow-up of 35 months (range, 4-108), TC was achieved in 96% of patients (n = 148/154) and at 3 and 5 years was 99% and 93%. Eighty-seven patients had serviceable hearing at the time of FSRT and evaluable audiometric follow-up. Overall HP was 67% and at 3 and 5 years was 66% and 54%. Pure tone average decreased by a median of 13 dB in all patients. Nineteen percent (n = 31) of patients experienced symptom improvement, and 8% (n = 13) had worsening of symptoms. Cranial nerve dysfunction occurred in 3.8% of patients (n = 6).

Reduced-dose FSRT to 46.8 Gy for AN achieves excellent functional HP rates and limited toxicity without compromising long-term TC. Based on these promising outcomes, further attempts at dose deescalation may be warranted.