The Role of Stereotactic Radiosurgery in the Management of Foramen Magnum Meningiomas—A Multicenter Analysis and Review of the Literature

Abstract

Background: Foramen magnum meningiomas (FMMs) represent a considerable neurosurgical challenge given their location and potential morbidity. Stereotactic radiosurgery (SRS) is an established non-invasive treatment modality for various benign and malignant brain tumors. However, reports on single-session or multisession SRS for the management and treatment of FMMs are exceedingly rare. We report the largest FMM SRS series to date and describe our multicenter treatment experience utilizing robotic radiosurgery. Methods: Patients who underwent SRS between 2005 and 2020 as a treatment for a FMM at six different centers were eligible for analysis. Results: Sixty-two patients met the inclusion criteria. The median follow-up was 28.9 months. The median prescription dose and isodose line were 14 Gy and 70%, respectively. Single-session SRS accounted for 81% of treatments. The remaining patients received three to five fractions, with doses ranging from 19.5 to 25 Gy. Ten (16%) patients were treated for a tumor recurrence after surgery, and thirteen (21%) underwent adjuvant treatment. The remaining 39 FMMs (63%) received SRS as their primary treatment. For patients with an upfront surgical resection, histopathological examination revealed 22 World Health Organization grade I tumors and one grade II FMM. The median tumor volume was 2.6 cubic centimeters. No local failures were observed throughout the available follow-up, including patients with a follow-up ≥ five years (16 patients), leading to an overall local control of 100%. Tumor volume significantly decreased after treatment, with a median volume reduction of 21% at the last available follow-up (p < 0.01). The one-, three-, and five-year progression-free survival were 100%, 96.6%, and 93.0%, respectively. Most patients showed stable (47%) or improved (21%) neurological deficits at the last follow-up. No high-grade adverse events were observed. Conclusions: SRS is an effective and safe treatment modality for FMMs. Despite the paucity of available data and previous reports, SRS should be considered for selected patients, especially those with subtotal tumor resections, recurrences, and patients not suitable for surgery.

Outcomes following stereotactic radiosurgery for foramen magnum meningiomas: a single-center experience and systematic review of the literature

“…In one study, 3 these patients were administered a median marginal dose of 20.0 Gy in 5 sessions and a median maximum dose of 45.0 Gy, at a median isodose line of 45%. In the other study, 9 these patients were administered a median marginal dose of 21.0 Gy in 3-5 sessions, and tumor volumes were significantly larger (median volume 5.3 vs 2.1 cm 3 ; p < 0.01) than those in patients undergoing singlefraction treatment.…”

“…The weighted median time to regression was 18 months from 3 studies 3,19 (including ours) with available data. The 3 largest studies calculated PFS rates and reported 5-year PFS rates of 100%, 3 93%, 9 and 92%. 19 PFS at 10 years remained at 100% 3 and 92% 19 in the 2 studies with available data.…”

“…Until 2018, relatively little had been documented about the application and outcomes following SRS for FMMs aside from 1 study 12 of 21 patients at a single institution, case reports, and small series of fewer than 10 patients. 14,18 Since 2018, 3 larger-cohort studies 3,9,19 have been published regarding outcomes following SRS for FMMs. These recent publications may suggest that although SRS treatment for FMMs has been historically underutilized, it is more recently gaining traction and recognition as an important treatment option.…”

“…Additionally, SRS application to this anatomical location is constrained by the brainstem dose (generally up to 12 Gy is tolerated) and inability to treat below the foramen magnum for lesions that extend into the cervical spine. 3,9 Last, there were no control cohorts in any of these studies, although it would have been useful to compare the rates of clinical stability and LC to those for patients undergoing resection or surveillance.…”

“…Rates of permanent morbidity and peri-or postoperative mortality can be as high as 15%-50% and 0%-25%, respectively. [7][8][9] Morbidity can be significant, including dysphagia requiring a permanent feeding tube or difficulty handling secretions requiring tracheostomy. Greater tumor volume, vertebral artery encasement, subtotal resection, pathological mitoses, and ventral/ventrolateral location have been previously identified as risk factors for postoperative complications following resection of FMMs.…”