Long-Term Tumor Control Following Gamma Knife Radiosurgery for Parasagittal Meningiomas: A Single Institution Retrospective Analysis

Introduction: Parasagittal meningiomas present unique challenges due to their proximity to large draining veins and the superior sagittal sinus, limiting the ability to achieve gross total resection (GTR). There is limited literature regarding the long-term efficacy of Gamma Knife Radiosurgery (GKSRS) for tumor control in this progression-prone region. We evaluated the effectiveness of GKSRS in achieving tumor control for parasagittal meningiomas. Methods: A retrospective analysis was conducted at a single academic institution from 2015 to 2023, analyzing predictors of progression via univariable and multivariable Cox regression analyses. Results: 30 patients were included. The median age was 62.0 years (range: 33–86). 86.7% underwent surgical resection prior to GKSRS. At presentation, 14 patients (46.7%) had primary tumors, while 16 (53.3%) had recurrent tumors. The median tumor volume was 2.0 cm³, and median tumor diameter was 1.7 cm. The median follow-up period was 33.0 months; mortality rate at last follow-up was 16.7%. 24 patients (80%) were treated with 1 fraction, while 6 (20%) were treated with 5 fractions. The median total GKSRS dose was 1500.0 cGy. At last follow-up, 80% of patients exhibited local tumor control. Peritumoral edema was present in 1 (3.3%) patient prior to GKSRS, with no cases observed following treatment. Median progression-free survival (PFS) was 70.6 months. Kaplan–Meier analysis demonstrated that WHO grade I meningiomas had longer mean PFS compared to grade II or III tumors (78.5 vs. 32.4 months, p = 0.011). In univariable Cox regression, age was associated with significantly greater risk of progression (HR: 1.2, p = 0.028). This remained significant in multivariable analysis after adjusting for tumor volume and tumor type (primary vs. recurrent) (HR: 1.2, p = 0.036). Tumor volume, radiation dose, extent of resection, and tumor type were not significantly associated with progression in either analysis. Conclusion: Our study provides supporting evidence for the use of GKSRS in achieving long-term tumor control for parasagittal meningiomas, with a tumor control rate of 80.0% and median PFS of 70.6 months. While increased age at the time of radiation and WHO grade appeared to be associated with progression in our analysis, these findings should be interpreted cautiously given the limited sample size. Notably, only 1 case of post-GKSRS edema was observed. These findings reinforce the safety and efficacy of GKSRS for this progression-prone region, though further multi-institutional studies are warranted to validate our results.