2025 Poster Presentations
P460: A COMPARATIVE STUDY OF FRAME-BASED VS MASK-BASED FIXATION FOR GAMMA KNIFE TREATMENT OF VESTIBULAR SCHWANNOMA
Ishav Shukla, BS; Jeffrey I Traylor, MD; Zabi Wardak, MD; Rance Fujiwara, MD; Walter Kutz, MD; Brandon Isaacson, MD; Ankur Patel, MD; Samuel Barnett, MD; University of Texas Southwestern Medical Center
Introduction: Gamma knife radiosurgery (GK) is a well-established treatment for vestibular schwannomas. Traditionally, a rigid stereotactic Leksell reference frame has been used for GK treatment to ensure accuracy, however, frameless thermoplastic mask-based fixation is offered by the new Gamma Knife Icon (Elekta AB, Stockholm, Sweden) machine and has grown in popularity due to improved patient comfort and a streamlined workflow. Previous studies have investigated the utility of these fixation techniques in patients with brain metastases undergoing GK, but this is the first study to our knowledge comparing their use in patients with vestibular schwannoma. This study aims to compare the recurrence rates and time to recurrence of vestibular schwannomas treated with GK using frame-based versus face mask-based fixation.
Methods: A retrospective analysis was conducted on patients with vestibular schwannomas treated with GK at UT Southwestern Medical Center between 2015 and 2022. Patients were divided into two groups based on the immobilization technique: frame-based and mask-based. Recurrence was defined as tumor growth on follow-up imaging as determined by a faculty otologist or neurosurgeon at our institution. Statistical analyses, including Logistic Regression and Cox Proportional Hazards Regression were performed to compare recurrence rates, time to recurrence, and associated risk factors between the two groups.
Results: The analysis included 82 patients with a mean age of 72.4 years (SD = 9.9), of which 47 (57.3%) were females. Frame-based fixation was used in 60 patients (73.2%) and mask-based in 22 patients (26.8%). The mean tumor diameter was 15.7 mm (SD = 6.9), and the mean dosage was 13.2 Gy (SD = 3.5). There was not a significant difference in mean tumor diameter between the two groups (17.65 mm (SD = 5.72) and 16.43 mm (SD = 6.75) for the frame group and mask group, respectively; p = 0.456). Recurrence was observed in 7 patients (8.5%), with 5 recurrences (8.3%) in the frame group and 2 recurrences (9.1%) in the mask group. There was no significant association between immobilization type and recurrence on multivariate logistic regression analysis (OR = 0.679, 95% CI: 0.068-6.704, p = 0.74). Additionally, Cox Regression analysis indicated that the type of fixation was not a significant predictor of time to recurrence (HR = 0.794, 95% CI: 0.091-6.901, p = 0.834).
Conclusion: No significant difference in recurrence rates or time to recurrence of vestibular schwannomas was found between frame-based and mask-based fixation techniques. The findings suggests that both immobilization methods are equally effective for GK in terms of tumor recurrence. The choice of immobilization technique can therefore be guided by other factors such as patient comfort, procedural efficiency, and need for repeatability.