Volumetric and Linear Imaging Response After Stereotactic Radiotherapy for Vestibular Schwannoma

SRT achieved durable control of VS across SRS, HFSRT, and FSRT in this single-institution cohort, with few salvage interventions. The three-axis volumetric criterion (20% increase) outperformed the MLD 2 mm threshold and correlated strongly with contoured gross tumor volume (GTV). Early progression subsided by 24 months, and stability at 12 and 24 months predicted five-year control. Between-regimen divergence at 24 months was consistent with SRS-driven pseudoprogression, with five-year progression remaining similar across regimens. Baseline imaging offered limited prognostic value, whereas clinical worsening, mainly hearing decline, correlated with volumetric progression. Annual MRI after year 1 is generally adequate, with tighter intervals reserved for selected patients. Prospective, audiometry-standardized studies are warranted for validating hearing-related endpoints.