Multicentric Evaluation of Long-term Outcome After Highly Advanced Single-Dose or Fractionated Radiation Therapy in Patients With Vestibular Schwannomas: Pooled Results From 3 Large German Centers

To evaluate long-term clinical outcome and prognostic factors for local-control, hearing preservation and cranial nerve toxicity in 449 patients treated for 451 vestibular schwannomas (VS) with radiosurgery (n = 169; 38%) or fractionated stereotactic radiation therapy (FSRT; n = 291; 62%). Two hundred forty-five patients were male (55%), and 204 were female (45%). Median age was 60 years (range, 17-88 years). Two hundred ninety-one patients (65%) were treated with FSRT, 160 (35%) with SRS. Median tumor diameter was 15 mm (range, 3-58 mm). Clinical symptoms included tinnitus in 219 patients (49%), facial impairment in 61 patients (14%), trigeminal neuralgia in 67 patients (15%) and vertigo in 197 patients (44%). For FSRT, a median dose of 57.6 Gy (range, 25-66 Gy) in median single doses of 1.8 Gy was applied. For SRS, median dose was 13 Gy (range, 10-20 Gy). The median follow-up time was 67 months (range, 2-252 months). Local control was 97% at 36 months, 95% at 60 months, and 94% at 120 months after treatments. There was not statistical difference between FSRT and SRS (p = 0.39). We classified Gardner-Robertson-Class I and II as “useful hearing”, which was present prior to RT in 207 patients (46%) at risk for hearing deterioration. Of these, 139 (67%) were treated with FSRT, and 68 (33%) with SRS. After RT, “useful hearing” was preserved in 85% of these patients. In 31 patients, hearing deteriorated into the class “non-useful-hearing” (Gardner-Robertson Class III-V), of these patients, 20 were treated with FSRT, and 11 with SRS. Thus, loss of useful hearing was observed in the FSRT group in 14%, and in the SRS group in 16% of the patients. Within the SRS group two patients were treated with single doses above 13 Gy (16 Gy and 20 Gy). Excluding these patients, useful hearing deterioration was 13%. Trigeminal nerve toxicity developed in 7 patients, of which 3 were treated with SRS; in two of these patients doses above 13 Gy were prescribed. Excluding these patients, trigeminal nerve toxicity rate was 1%. There was no difference between FSRT and SRS. For facial nerve toxicity, 8 patients developed new symptoms, of which 3 were treated with FSRT and 5 with SRS (of which 4 received doses above 13 Gy). Excluding these 4 patients, facial nerve toxicity rate was about 1%, respectively. Supported by this large multicentric series, both SRS and FSRT can be recommended for the treatment of VS. SRS application is limited by tumor size due to the known increase in unwanted effects in larger volumes. SRS follows a steep dose-response-curve, and doses above 13 Gy are associated with a pronounced increase in toxicity. When chosen diligently based on tumor volume, pre-treatment characteristics and volume-dependent dose-prescription in SRS, both treatments may be considered equally effective.