ESTRO 2025 - Abstract Book

S753

Clinical - CNS

ESTRO 2025

Keywords: Pituitary adenomas

References: 1. Gupta T, Chatterjee A. Modern Radiation Therapy for Pituitary Adenoma: Review of Techniques and Outcomes. Neurol India. 2020 May-Jun;68:S113-S122. 2. Kowalchuk RO, Trifiletti DM, Brown PD, Sheehan JP. Contemporary radiotherapy and radiosurgery techniques for refractory pituitary adenomas. Pituitary. 2023 Jun;26(3):298-302. 3. Li X, Li Y, Cao Y, Li P, Liang B, Sun J, Feng E. Safety and efficacy of fractionated stereotactic radiotherapy and stereotactic radiosurgery for treatment of pituitary adenomas: A systematic review and meta-analysis. J Neurol Sci. 2017 Jan 15;372:110-116.

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Digital Poster Predictive Factors for Radiation-Induced Facial Spasms, Toxicities, and Long-Term Outcomes of Stereotactic Radiotherapy in Vestibular Schwannoma M. Berckenbosch 1 , J. J. Waterval 2,3 , D. H.P.M. Kunst 2,3,4 , K. Hovinga 3,5 , Y. Temel 3,5 , R. Houben 1 , C. M.L. Zegers 1 , D. B.P. Eekers 1,3 , I. Compter 1,3 1 Department of Radiation Oncology, Maastro, Maastricht, Netherlands. 2 Department of Otorhinolaryngology, Maastricht University Medical Centre, Maastricht, Netherlands. 3 Dutch Academic Alliance Skull Base Pathology, Maastricht University Medical Centre, Maastricht/Nijmegen, Netherlands. 4 Department of Otorhinolaryngology, Radboud University Medical Centre, Nijmegen, Netherlands. 5 Department of Neurosurgery, Maastricht University Medical Centre, Maastricht, Netherlands Purpose/Objective: Stereotactic radiotherapy (SRT) is a minimally invasive technique delivering high-dose, targeted radiation in single or multiple sessions. In treating vestibular schwannoma (VS), SRT may lead to toxicities such as facial spasms and neuropathies. This study aims to identify predictive factors for these complications, assess local tumor control across different fractionation regimens, and evaluate long-term outcomes to enhance clinical decision-making. Material/Methods: A retrospective analysis was conducted on 133 VS patients treated with linac-based SRT at a single institution between August 2015 and July 2024. Fractionation schedules included 1×12Gy, 5×5Gy, and 26×1.8Gy, selected based on tumor characteristics and Koos grade. Patient demographics, tumor features, and treatment parameters were analyzed. Logistic regression was used to identify predictors of facial spasms, other toxicities, and local tumor control. Statistical significance level alpha was set at 0.05. Results: Patients were distributed across Koos grades: Grade I (3.8%), Grade II (48.1%), Grade III (18.8%), and Grade IV (29.3%). Median follow-up was 33 months (range 0–103). Nineteen (14.3%) patients underwent prior SRT partial tumor resection. The 3- and 5-year local tumor control rates were 92.5% and 90.2%, respectively. Pseudoprogression, defined as a transient increase in tumor volume within 2 years after treatment, was observed in 34 patients (25.6%). Median tumor volume and patient age were 1.41 cm³ (0.2 – 24.6) and 63 years (25 – 86). Acute side effects included headache (51.1%), fatigue (28.6%), balance disturbances (27.8%), tinnitus (17.3%), and nausea/vomiting (12.8%), most of which were typically managed with corticosteroids. Post-SRT, 21 patients (15.8%) developed new-onset facial symptoms, including hemifacial spasms in 18 (13.5%), with female gender identified as the sole predictive factor (OR: 7.663, p=0.035). Other toxicities included hearing loss (11.8%), balance deterioration (30.8%), trigeminal neuropathy (6%), and abducens neuropathy (1.5%). No significant differences in outcomes were observed between fractionation regimens or Koos grades.