2026 Poster Presentations
P150: FRAME-BASED VERSUS FRAMELESS GAMMA KNIFE RADIOSURGERY FOR UPFRONT TREATMENT OF INTRACRANIAL MENINGIOMA
Misha Amini, MD; Anthony J Tang, BBA, BSA; Charles T Borchers, BS; Arjun R Adapa, MD; Eric Giannaris; Michael B Sisti, MD; Jeffrey N Bruce, MD; Brian J Gill, MD; Brett E Youngerman, MD; Guy M McKhann, MD; Tony J Wang, MD; Matthew Gallitto, MD, PhD; Columbia University Irving Medical Center
Background: Gamma Knife radiosurgery is a commonly used upfront treatment of intracranial meningioma. Immobilization is an essential aspect of GKRS due to high doses of radiation and minimal margins of error with surrounding brain. Traditionally, immobilization was performed using a stereotactic frame that is placed under local anesthesia and remains in place during planning and treatment; however, this can lead to discomfort, and complications such as infections and persistent pain at the insertion site have been reported. Beginning in 2016, our institution adopted the frameless technique (The GK Icon) using a lightweight plastic mask for immobilization, allowing for enhanced patient comfort as well as fractionation of treatments over several days. We report long-term outcomes comparing frameless versus frame-based fixation.
Methods: We conducted a retrospective cohort study of patients with intracranial meningioma treated with GKRS at our institution (2014 to 2021) for upfront management of meningioma using frame-based or frameless (mask) head fixation. The primary endpoint was progression-free survival (PFS) from GKRS to radiographic local failure or death. Overall survival (OS) was defined from GKRS to death. Survival was estimated with Kaplan-Meier, reported as median and 1-, 3-, and 5-year rates with 95% confidence intervals, and compared between fixation groups using the log-rank test; median follow-up was estimated using reverse Kaplan-Meier. Secondary outcomes included symptomatic toxicity, use of steroids or Avastin, optic neuropathy, and new tumor, which were modeled with logistic regression, estimating odds ratios for the frame versus mask cohorts and adjusting for age at GKRS, follow-up duration, and pathology grade (when available); p-values were corrected using the Benjamini-Hochberg method. Baseline characteristics were tabulated including sex, age at treatment, and GKRS parameters such as total dose and number of fractions.
Results: 134 lesions in 123 patients were analyzed (Mask n = 80, Frame n = 54). Median follow-up was 56.1 months: Mask 54.1; Frame 73.0. Tumor grade was available for post-operative lesions (n=30): WHO I 43%; WHO II 57%. Median PFS was 100.4 months in the Mask cohort and unreached in the Frame cohort; PFS did not differ by fixation (log-rank p=0.40). One-, three-, and five-year PFS were: Mask 100.0% / 94.5% (89.5–99.9) / 92.0% (85.2–99.3); Frame 96.2% (91.2–100.0) / 91.7% (84.3–99.9) / 78.8% (67.2–92.4). For OS, there were 3 deaths in the mask group and 2 in the frame group, with no difference by fixation (log-rank p=0.60). One-, three-, and five-year OS were: Mask 100.0% / 97.4% (93.8–100.0) / 97.4% (93.8–100.0); Frame 100.0% / 100.0% / 93.9% (86.1–100.0). Median OS was not reached in either group. Analyses of secondary outcomes showed no significant differences between groups after multiple-testing correction.
Conclusion: In this single-institution cohort of 134 lesions, framed versus frameless head immobilization during upfront GKRS treatment was not associated with differences in PFS or OS. After adjusting for age, follow-up time, and tumor grade, no significant differences were found in secondary outcomes. These findings support frameless mask immobilization for GKRS in upfront treatment of meningioma as a viable alternative to frame fixation without compromising survival or measured toxicities.