Single-fraction vs. fractionated linac-based stereotactic radiosurgery for vestibular schwannoma: a single-institution study

PURPOSE: In this single-institution trial, we investigated whether fractionated stereotactic radiation therapy is superior to single-fraction linac-based radiosurgery with respect to treatment-related toxicity and local control in patients with vestibular schwannoma. METHODS AND MATERIALS: All 129 vestibular schwannoma patients treated between 1992 and June 2000 at our linac-based radiosurgery facility were analyzed with respect to treatment schedule. Dentate patients were prospectively selected for a fractionated schedule of 5 x 4 Gy and later on 5 x 5 Gy at the 80% isodose in 1 week with a relocatable stereotactic frame. Edentate patients were prospectively selected for a nonfractionated treatment of 1 x 10 Gy and later on 1 x 12.5 Gy at 80% isodose with an invasive stereotactic frame. Both MRI and CT scans were made in all 129 patients within 1 week before treatment. All patients were followed yearly with MRI and physical examination. RESULTS: A fractionated schedule was given to 80 patients and a single fraction to 49 patients. Mean follow-up time was 33 months (range: 12-107 months). There was no statistically significant difference between the single-fraction group and the fractionated group with respect to mean tumor diameter (2.6 vs. 2.5 cm) or mean follow-up time (both 33 months). Only mean age (63 years vs. 49 years) was statistically significantly different (p = 0.001). Outcome differences between the single-fraction treatment group and the fractionated treatment group with respect to 5-year local control probability (100% vs. 94%), 5-year facial nerve preservation probability (93% vs. 97%), and 5-year hearing preservation probability (75% vs. 61%) were not statistically significant. The difference in 5-year trigeminal nerve preservation (92% vs. 98%) reached statistical significance (p = 0.048). CONCLUSION: Linac-based single-fraction radiosurgery seems to be as good as linac-based fractionated stereotactic radiation therapy in vestibular schwannoma patients, except for a small difference in trigeminal nerve preservation rate in favor of a fractionated schedule.