Outcomes of repeat stereotactic radiosurgery for recurrent or progressive sporadic vestibular schwannoma: a multicenter international study

Abstract

Background and objectives: Repeat stereotactic radiosurgery (SRS) is a noninvasive option for recurrent vestibular schwannoma (VS). This study evaluates outcomes in patients with long-term follow-up. Methods: This retrospective multicenter study analyzed 81 patients with recurrent unilateral sporadic VS after initial SRS, with ≥12 months of follow-up. Outcomes included tumor control, hearing preservation, cranial nerve function, and adverse radiation effects (ARE). Kaplan-Meier and Cox regression identified factors affecting outcomes. Results: The median age at the second SRS was 60 years, with a median interval of 58 months between procedures. The median margin doses were 12.0 Gy (single-fraction), 17.25 Gy (3-fraction), and 25 Gy (5-fraction). Tumor control was achieved in 69 patients (85.2%), with 5- and 10-year local control rates of 82% and 76.5%, respectively. Significant predictors of local failure included tumor volume >2.2 cm3 (area under the curve = 0.757, P = .018), prescription biological effective dose (BED) ≤70.3 Gy (hazard ratio [HR]: 0.89, P = .003), and interval between treatments >27.5 months (HR: 1.02, P = .015). In single-fraction SRS, higher prescription dose reduced failure risk (HR: 0.31, P = .002) with a margin dose ≥12 Gy being critical for improved tumor control (P < .001). Serviceable hearing was retained in 12 of 18 cases (66.7%), and facial nerve function was preserved in 72 of 80 cases (90%). ARE occurred in 11 patients (13.6%), most commonly perilesional edema (63.7%). ARE correlated with higher brainstem maximum BED in the entire cohort (HR: 1.02, P = .016) and in single-fraction SRS (HR: 1.02, P = .006). Pseudoprogression (9.8%) was linked to younger age (HR: 0.88, P = .023) and shorter time between SRS (HR: 0.87, P = .012). Conclusion: Repeat SRS is an effective option for recurrent sporadic VS, offering high tumor control and functional preservation. Outcomes depend on age, interval between treatments, tumor volume, and BED. With careful planning, adverse effects are rare and typically transient.