Basis for Immunotherapy for Treatment of Sporadic Vestibular Schwannoma

Vestibular schwannoma (VS) is managed with observation, surgery, or radiation, but treatment-refractory cases pose significant clinical challenges. With recurrence rates of 30.7% after subtotal resection and 5 to 15% radiation failure rates, salvage therapies carry substantial morbidity, including facial nerve injury (30–50%) and cerebrospinal fluid leak (15–20%), highlighting the urgent need for novel therapeutic approaches. Narrative review of current literature. Literature review of published clinical reports, early-phase trials, and translational research studies in VS. Patients with VS and experimental tumor models. Tumor growth control, recurrence rates, characterization of the VS tumor microenvironment, and evaluation of immunotherapeutic strategies. The VS tumor microenvironment provides a compelling rationale for immunotherapy, with tumor-associated macrophages comprising up to one-third of tumor mass in aggressive cases. Merlin-deficient tumor cells upregulate PD-L1 and secrete cytokines (M-CSF, TNF-α, IL1β, IL-6) that create a paradoxically inflammatory yet immunosuppressive microenvironment through T-cell anergy and sustained PD1/PD-L1 engagement. Although clinical evidence remains limited, consisting of isolated case reports and a single small uncontrolled pilot trial in NF2-associated disease, preliminary results provide hypothesis-generating data. Theoretical and preclinical strategies under early investigation include CAR-T cell therapy, combination checkpoint blockade with anti-angiogenics, and novel delivery platforms for enhanced skull base access. Biomarker development remains critical for patient selection, with candidates including PD-L1 expression, tumor-infiltrating lymphocyte profiles, and dynamic markers like treatment-induced regulatory T cell depletion. Success requires multi-institutional collaboration, adaptive trial designs, and rational combination strategies addressing the complex immunosuppressive mechanisms within VS. While the biological rationale is compelling, the field remains in an exploratory phase with no firm therapeutic conclusions possible at this stage. Rigorous prospective investigation is needed before immunotherapy can be considered a viable treatment strategy for sporadic VS.