Radiotherapy for Growing Vestibular Schwannomas

CLINICAL QUESTION: What is the long-term tumor-control outcome of radiotherapy in patients with radiologically growing vestibular schwannomas (VS), and are pre-treatment tumor size or location associated with treatment failure?

BOTTOM LINE: Radiotherapy achieved durable tumor control in most growing vestibular schwannomas, with outcomes unaffected by pre-treatment tumor size or location.

BACKGROUND: Vestibular schwannomas are benign, slow-growing tumors of the eighth cranial nerve that can cause hearing loss, tinnitus, and imbalance. Although stereotactic radiosurgery (SRS) and fractionated stereotactic radiotherapy (FSRT) yield tumor-control rates above 90% in mixed VS cohorts, prior studies rarely separated stable from growing tumors. This analysis focused exclusively on radiologically progressing VS to clarify radiotherapy efficacy in a higher-risk population.

STUDY DESIGN: This multicenter international study used prospectively collected data from eight tertiary skull base referral centers in England, Italy, the Netherlands, and the U.S. between January 1, 2000, and September 30, 2023. Patients had sporadic unilateral VS with confirmed radiologic growth (≥2 mm) before first-line radiotherapy. Primary tumor control was defined as an increase in intracranial tumor diameter of ≥3 mm within two years or ≥2 mm thereafter to account for post-radiotherapy pseudoprogression.

SETTING: Data were obtained from Cambridge University Hospitals, Oxford University Hospitals, Guy’s and St Thomas’ NHS Foundation Trust, the National Hospital for Neurology and Neurosurgery, Salford Royal Foundation Trust, Mayo Clinic (USA), Vicenza Hospital (Italy), and Maastricht University Medical Centre (Netherlands).

SYNOPSIS: Among 1,883 patients (median age 63 years; 52% female), the median pre-treatment tumor size was 14 mm, and 86.9% had extracanalicular lesions. Most of these patients received Gamma Knife or CyberKnife SRS. The 10-year tumor-control rate was 76.1% (95% CI, 72.7–79.2%), with no significant associations between tumor size or location and treatment failure. Alternative definitions yielded control rates from 60% (≥2 mm criterion) to 93% (conversion-to-surgery endpoint). Further, median follow-up was 3.6 years (IQR 1.8–6.4). In these patients, most progression occurred within the first two years, with only 6.6% of early enlarging tumors showing continued growth after three years. Radiotherapy, therefore, provided durable, size-independent tumor control for actively growing VS. The authors noted that higher control rates reported in prior literature likely reflect inclusion of non-growing tumors. Strengths of this study included the large, internationally representative dataset, while limitations involved moderate follow-up duration, absence of volumetric analyses, and variation in imaging and radiotherapy protocols among centers.

CITATION: Sethi M, et al. Radiotherapy for growing vestibular schwannomas. JAMA Otolaryngol Head Neck Surg. 2025;151:931-937. doi:10.1001/ jamaoto.2025.1953

COMMENT: This prospective international study evaluated long-term tumor control rates in patients with growing vestibular schwannomas that were treated with first-line radiotherapy. This study stands out because it only includes tumors with documented pre-treatment growth (unlike many other studies, which also include non-growing tumors) and because of the large multicenter cohort of patients analyzed. This allows for a more precise assessment of the efficacy of radiotherapy in growing tumors, including the analysis of treatment failure based on different thresholds of tumor growth and surgical conversion.—Robert Hong, MD