The impact of biologically effective dose on volumetric decrease after upfront stereotactic radiosurgery for intracranial meningiomas

Introduction Stereotactic radiosurgery (SRS) is a valuable treatment option for small to medium-sized meningiomas. Research question The primary outcome was to assess tumor volumetric decrease over time as a function of BED Gy2.47 . BED Gy2.47 was also analysed by using 5 different subcategories. Materiel and Methods Between July 2010 and August 2023, 261 consecutive intracranial meningiomas were treated by upfront radiosurgery. Serial follow-up MRI was used to manually contour tumor volumes at 6, 12, 24, 36, 60, 84, 120, 144 and 168 months. Median follow-up was 60 months (mean 58.6; range: 6–168). A total of 1324 volumes were delineated. Radiosurgical parameters were assessed, including biologically effective dose (BED Gy2.47 ). Results An increase of 1 unit in BED resulted in a less significant volumetric reduction over the follow-up period (p < 0.0001). Among BED Gy2.47 subcategories, the most statistically significant effects were observed in the 40–49.9, 50–59.9, and 60–69.9 groups. In univariate analysis, cavernous sinus meningiomas had the most important volumetric decrease. The greatest BED-related impact on volume reduction was observed in tentorial, cavernous sinus, convexity, parasagittal, skull base, and posterior fossa regions (in decreasing order). Physical dose was not statistically significant (p = 0.4). Significant predictors of volume reduction included radiation dose rate (p < 0.0001), gradient index (p = 0.02), and the number of isocenters (p < 0.0001) Discussion and Conclusion BED Gy2.47 is relevant for volumetric decrease after upfront radiosurgery for intracranial meningiomas. Physical dose was not statistically significant. Certain anatomical regions may be more radiosensitive or respond more favorably to optimized BED delivery.