Risk of Internal Carotid Artery Stenosis or Occlusion after Single-Fraction Radiosurgery of Benign Parasellar Tumors

Introduction: Stereotactic radiosurgery (SRS) is an accepted treatment option for patients with benign parasellar tumors. Our objective was to determine the risk of developing new or progressive internal carotid artery (ICA) stenosis/occlusion after single-fraction SRS of cavernous sinus meningiomas (CSM) or growth-hormone secreting pituitary adenomas (GHA).

Methods: Retrospective review of 283 patients (155 CSM/128 GHA) treated with single-fraction SRS, 1990 to 2015. Study criteria included no prior irradiation and ≥12 months of post-SRS radiologic follow-up. Pre-SRS grading of ICA involvement was as described by Hirsch (1993) for CSM or Knosp’s (1993) for GHA. Ninety-three (60%) CSM had Hirsch’s grade II and III tumors; 97 (76%) GHA had Knosp’s grade II to IV tumors.

Results: Median follow-up after SRS was 6.6 years (range, 1–24.9). No GHA or grade I CSM developed ICA stenosis/occlusion. Three grade II CSMs (5.2%) had asymptomatic ICA stenosis (n = 2) or occlusion (n = 1); 1 (1.1%) had transient ischemic symptoms. Five grade III CSM (14.3%) progressed to ICA occlusion (4 asymptomatic, 1 symptomatic). Median time to stenosis/occlusion was 4.8 years (range, 1.8–7.6). Five- and 10-year risks of ICA stenosis/occlusion in grade II/III CSM were 7.5 and 12.4%. Five- and 10-year risk of ischemic stroke from ICA stenosis/occlusion in grade II/III CSM was 1.2%. Multivariable analysis found patient age (HR = 0.92; 95% CI 0.86–0.98; p = 0.01), meningioma pathology (HR, 95% CI not defined; p = 0.03), and carotid grade (HR = 4.51; 95% CI = 1.77–14.61; p = 0.004) to be associated with ICA stenosis/occlusion. ICA stenosis/occlusion was not related to post-SRS tumor growth (HR, 95% CI not defined; p = 0.41).

Conclusion: New or progressive ICA stenosis/occlusion was common after SRS for CSM but was not observed after SRS for GHA, suggesting a tumor-specific mechanism not related to radiation dose. Pre-SRS ICA encasement/constriction increases the risk of ICA stenosis/occlusion, however, the risk of ischemic complications is very low.