Long-term Outcomes and Patterns of Tumor Progression After Gamma Knife Radiosurgery for Benign Meningiomas

Abstract

GKRS demonstrates excellent long-term tumor control in the management of benign meningiomas. Tumor progression occurred at a mean time of 7.5 years after GKRS, reinforcing the need for long-term surveillance despite initial tumor control. Treatment failure was related to undercoverage of lesions in the majority of cases, with the remainder demonstrating evidence of abnormal tumor biology.

Predictors of response to Gamma Knife radiosurgery for intracranial meningiomas

“…2,20,23,31,47,50 While meningioma location within the convexity or parasagittal regions, larger tumor volume, and greater radiation dosing appear to be factors that are often predictive of an increased risk of edema, none of these variables were found to be significant in our study. 2,31,50 In the study by Patil et al, where edema was similarly defined based on new T2 signal changes on MRI, close to one-third of patients harbored meningiomas that were within the parasagittal region. Similarly, Chang et al 2 demonstrated that tumor location within the convexity region was significantly predictive of post-SRS T2 signal changes.…”

“…Similarly, Chang et al 2 demonstrated that tumor location within the convexity region was significantly predictive of post-SRS T2 signal changes. Zada et al, 50 using a similar definition of edema, showed that lesion volume was almost double in patients who developed post-SRS edema in comparison with patients without SRS-edema (11 vs 5.7 cm 3 ). The incidence of edema in our study, however, was similar regardless of tumor location (basal or nonbasal).…”

“…6,7,9,10,15,18,19,29,31,42,44,50 Therefore, the new onset of any of the aforementioned complications in each patient following SRS was documented and analyzed. The development of any new T2 or FLAIR signal changes surrounding the lesion following SRS were interpreted as edema.…”

“…12,17,18,20,21,32,33 While SRS minimizes many of the morbidities associated with aggressive resection, delayed adverse outcomes such as radiation necrosis, cranial nerve neuropathies, occlusion of the venous structures, hydrocephalus, and edema are possible; the occurrence of these complications is approximately 10% in the reported literature, with variability depending on the cohorts of analyzed patients. 1,31,37,43,44,46,50 Post-SRS edema has been reported as an adverse effect/complication, which can result in neurological symptoms. Location (primarily the convexity and parasagittal regions) and larger initial tumor volume have also been associated with a higher risk of edema.…”

“…Location (primarily the convexity and parasagittal regions) and larger initial tumor volume have also been associated with a higher risk of edema. 2,17,31,50 The variability in tumor control rates is, for the most part, attributed to the heterogeneity of the patient population, tumor histology, WHO grade, tumor size at the time of treatment, institutional variations in radiation dosing, length of follow-up, and how tumor growth and control are established. In addition, however, most methods used for reporting control rates have been restricted to 2D diametric measurements-where arbitrary dimensions are sometimes selected-rather than true volumetric measurements, which are potentially a more accurate reflection of the extent of tumor growth.…”