Post Surgical Management of WHO Grade II Meningiomas: Our Experience, the Role of Gamma Knife and a Literature Review

Abstract

Purpose: Grade II meningiomas are rarer than Grade I, and when operated on, bear a higher risk of local recurrence, with a 5-year progression free survival (PFS) ranging from 59 to 90%. Radiotherapy (RT) or radiosurgery, such as Gamma Knife radiosurgery (GKRS) can reduce the risk of relapse in patients with residual disease, even if their role, particularly after gross total resection (GTR), is still under debate. Main goal of this study was to compare the outcomes of different post-surgical management of grade II meningiomas, grouped by degree of surgical removal (Simpson Grade); next in order we wanted to define the role of GKRS for the treatment of residual disease or relapse. Methods: from November 2016 to November 2020 all patients harboring grade II meningiomas, were divided into three groups, based on post-surgical management: (1) wait and see, (2) conventional adjuvant radiotherapy and (3) stereotactic GKRS radiosurgery. Relapse rate and PFS were registered at the time of last follow up and results were classified as stable, recurrence next to or distant from the surgical cavity. In the second part of the study we collected data of all patients who underwent GKRS in our Centers from November 2017 to November 2020. Results: A total of 37 patients were recruited, including seven patients with multiple meningiomas. Out of 47 meningiomas, 33 (70.2%) were followed with a wait and see strategy, six (12.7%) were treated with adjuvant radiotherapy, and 8 patients (17.0%) with adjuvant GKRS. Follow up data were available for 43 (91.4%) meningiomas. Within the wait and see group, recurrence rates differed based on Simpson grades, lower recurrence rates being observed in three Simpson I cases (30%) compared to twelve relapses (60%) in patients with Simpson grade II/III. Finally, out of the 24 meningiomas undergoing GKRS (8 residual and 16 recurrence), 21 remained stable at follow up. Conclusions: Gross total resection (GTR) Simpson II and III have a significantly worse outcome as compared to Simpson I. The absence of adjuvant treatment leads to significant worsening of the disease progression curve. Adjuvant radiotherapy, especially GKRS, provides good local control of the disease and should be considered as an adjuvant treatment in all cases where Simpson I resection is not possible.

Keywords: GKRS; Gamma Knife; Simpson grade; WHO grade II meningiomas; atypical meningiomas; radiosurgery.

Figure 1

Illustrative diagram of postoperative management for all meningiomas (first picture) and follow up of patients with only gross total resection (GTR), stratified by Simpson grade (second picture). It does not include GKRS treatments on relapse.

Figure 2

Kaplan–Meier for PFS (progression-free survival). PFS (months) is reported on the x axis, while on the y-axis shows the percentage of patients without relapse. In this case the event is represented by the presence of relapse. (A). Kaplan–Meier for patients undergoing wait and see (black line) and patients undergoing any adjuvant treatment (red line). Patients undergoing adjuvant treatment had a lower PFS than patients who received no treatment. This is explainable considering that the majority of patients subjected to a wait and see strategy had a GTR surgical removal while patients with adjuvant treatment only had an STR. (B). Kaplan–Meier progression-free survival for patients undergoing GTR (black line) and patients undergoing STR (red line). Partial surgical excision (Simpson IV–V), as represented by the univariate analysis, is the only significant risk factor for the presence of recurrence. (C) Kaplan–Meier progression-free survival for patients undergoing GTR—excluded Simpson grade I (red line) and patients undergoing STR (black line). In order to understand if PFS was greatly influenced by Simpson I patients, we deliberately excluded these patients from the curve and we saw that the PFS curve was reversed. This suggests that the Simpson II and III categories should be considered separately when assessing the likelihood of disease progression, especially with regard to decisions on possible adjuvant treatments.

Figure 3

MRI images of some representative cases. Patient with right fronto-parietal convexity meningioma (A), subjected to GTR (Simpson I), as can be seen from the post-operative brain MRI (B). Due to the pathological features (high number of mitoses and cerebral invasion) the patient underwent adjuvant RT treatment despite surgical removal Simpson I. Good local control after two years from adjuvant RT (C). After 36 months, appearance of distal recurrence (D). MRI of a patient with multiple meningiomas (E). Patient with large left frontal meningioma, subjected to surgical removal (F), associated with two other nodules at the left sphenoidal wing, subjected to GKRS (G). Picture (H) shows good disease control 4 years after GKRS treatment. GKRS for a small recurrence of left frontal convexity meningioma (I) and relative MRI control 18 months after (J). GKRS for two nodules of right fronto-temporal meningioma (K). 15 months after radiosurgery, a new GKRS was performed on a further nodule of recurrence at the sphenoidal wing (L).

Figure 3

MRI images of some representative cases. Patient with right fronto-parietal convexity meningioma (A), subjected to GTR (Simpson I), as can be seen from the post-operative brain MRI (B). Due to the pathological features (high number of mitoses and cerebral invasion) the patient underwent adjuvant RT treatment despite surgical removal Simpson I. Good local control after two years from adjuvant RT (C). After 36 months, appearance of distal recurrence (D). MRI of a patient with multiple meningiomas (E). Patient with large left frontal meningioma, subjected to surgical removal (F), associated with two other nodules at the left sphenoidal wing, subjected to GKRS (G). Picture (H) shows good disease control 4 years after GKRS treatment. GKRS for a small recurrence of left frontal convexity meningioma (I) and relative MRI control 18 months after (J). GKRS for two nodules of right fronto-temporal meningioma (K). 15 months after radiosurgery, a new GKRS was performed on a further nodule of recurrence at the sphenoidal wing (L).