Presenter(s)
M. Gribble1, D. P. I. Capaldi2, N. T. Jiam3, J. Chew2, J. L. Nakamura2, L. Boreta2, D. Raleigh4, S. E. Braunstein2, P. V. Theodosopoulos5, R. A. Morshed5, and H. Vasudevan2; 1University of California San Francisco, San Francisco, CA, 2Department of Radiation Oncology, University of California San Francisco, San Francisco, CA, 3University of California, San Francisco, Department of Otolaryngology - Head and Neck Cancer, San Francisco, CA, 4University of California San Francisco, Department of Radiation Oncology, San Francisco, CA, 5University of California San Francisco, Department of Neurological Surgery, San Francisco, CA
Purpose/Objective(s): SRS provides excellent control with limited toxicity for vestibular schwannomas, but evidence for cranial non-vestibular schwannomas is limited and toxicity may vary by location and treatment approach. Here, we evaluate the efficacy and outcomes of SRS for cranial non-vestibular schwannomas.
Materials/Methods: 34 patients with cranial non-vestibular schwannomas treated with SRS at a single institution between 2002 and 2025 were retrospectively identified. Tumors included facial nerve (n=11, 32%), jugular foramen (n=10, 29%), trigeminal (n=9, 26%), oculomotor (n=2, 6%), optic (n=1, 3%), and trochlear nerve schwannomas (n=1, 3%). Median age was 52 years (range 29-81), and 33/34 patients (97%) were symptomatic at diagnosis. Twenty patients (59%) received SRS alone, 12 (35%) underwent adjuvant SRS following subtotal resection (n=11) or biopsy (n=1), and 2 (6%) underwent salvage SRS >6 months after near complete resection. Median prescription dose was 12.5 Gy (range 12-13) for single-fraction treatment (n=28, 82%) and 25 Gy in 5 fractions for fractionated treatments (n=6, 18%). Median target volume was 1.68 cc (range 0.04-10.2 cc) for single fraction treatments and 2.29 cc (range 0.38-11.9 cc) for fractionated treatments.
Results: Tumor control was achieved in 32/34 patients (94%) with a median 36-month follow-up (range 6-150). No significant differences in progression rates were observed by tumor location (p=0.598), SRS fractionation (p=0.492), or target volume (p=0.943). Among 11 facial nerve schwannomas, facial nerve function improved in 27% (n=3, median 2 House-Brackmann [HB] grade improvement), remained stable in 55% (n=6), and transiently worsened in 18% (n=2), returning to within 1 HB grade of pre-treatment baseline at last follow up. Among 10 jugular foramen schwannomas, the most common presenting symptoms were dizziness/vertigo (70%, n=7), which improved in 6 of 7 patients post-treatment. Among 7 of 9 patients with trigeminal schwannomas who presented with facial numbness or dysesthesia, symptoms improved significantly in 57% (n=4), worsened or expanded in 29% (n=2), and remained stable in 14% (n=1). Symptom-free survival did not significantly differ by initial management, location, or fractionation, though fractionated treatment trended toward better symptom-free survival (66.7% vs 37.5%, p=0.134). Two patients (6%) with large post-surgical volumes (9.9, 10.2 cc) had Grade 2 cranial neuropathies within one month, improving with steroids. All treatment-related cranial neuropathies were stable or improved at last follow-up.
Conclusion: SRS provides excellent tumor control for symptomatic cranial non-vestibular schwannomas with minimal morbidity in both the upfront and postoperative setting. In this single-institution cohort, larger jugular foramen and trigeminal schwannomas were more frequently managed surgically with adjuvant SRS while smaller tumors and upper cranial nerve locations (II-IV) were effectively treated with upfront SRS.