P19.02 Clinical and radiological long term outcome of acoustic neuromas (Koos grade I - IV) after stereotactic radiosurgery

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AbstractIntroduction:In the management of acoustic neuroma (AN) stereotactic radiosurgery (SRS) has evolved as widely accepted treatment option for small-sized tumors (Koos I and II). For larger AN (Koos III and IV) microsurgery is treatment of choice. However, for patients not suitable for microsurgery SRS might also be an alternative that balances tumor control, hearing preservation and adverse effects. The purpose of this analysis was to evaluate the efficacy and toxicity of SRS for different Koos grades including AN Koos III and IV.Methods:In this single center retrospective analysis (1991 - 2015) we included all patients with previously untreated AN who underwent single session LINAC or Cyberknife® based SRS with a minimum follow-up of 3 months. Patient data were analyzed and correlated (Pearson`s coefficient) with the different Koos grades in terms of radiological tumor control, preservation of serviceable hearing, course of median pure tone averages (PTA) and adverse events rated by Common Terminology Criteria for Adverse Events (CTCAE; v4.03).Results:301 patients (f:m = 151:150, median age 59 years ±13.6, range 17–84) were identified with a mean follow-up of 50.9 months (range 3–265). Mean tumor volume was 1.85 ml ±2.4 (range 0.1–23.7, the mean marginal dose was 12.4 Gy ± 0.8 (range 11–20) and the prescription isodose was 69.3 % ± 12.5 (range 32.9–86.2). With regard to the Koos classification 52 patients were considered as grade I, 162 as grade II, 42 and 45 as grade III and IV, respectively.At last follow-up after SRS 94% of the patients showed radiological tumor control. There was no significant correlation (p < 0.113) between Koos grades I/II vs III/IV and radiological tumor control.Median PTA of Koos I/II tumors increased about 49% (37,2 dB prior to SRS up to 55,6 dB at last follow-up). In case of Koos III/IV tumors the increase of median PTA was similar (47%; 46,2 dB up to 68,2 dB).The rate of transient facial nerve dysfunction CTCAE grade 1 or 2 in Koos I/II tumors was 2.3% and 4.6% in Koos III/IV. Permanent facial nerve dysfunction CTCAE grade 1 was observed in one patient with Koos grade I and III, respectively. Transient trigeminal nerve impairment CTCAE grade 1/2 occurred with 3.7% in Koos I/II and with 6.9% in Koos III/IV. Four patients (4.6%) with Koos III/IV tumors had permanent trigeminal nerve impairment CTCAE grade 1/2.Conclusion:SRS for AN shows reliable long term tumor control and a high rate of hearing preservation and without considerable permanent side effects. Therefore, SRS can be proposed as safe and effective treatment option for AN, even with higher Koos grades.