Predictors of early progression of surgically treated atypical meningiomas

Abstract

Background: Clinical behaviour of atypical meningiomas is not uniform. While, as a group, they exhibit a high recurrence rate, some pursue a more benign course, whereas others progress early. We aim to investigate the imaging and pathological factors that predict risk of early tumour progression and to determine whether early progression is related to outcome.

Methods: Adult patients with WHO grade II meningioma treated in three regional referral centres between 2007 and 2014 were included. MRI and pathology characteristics were assessed. Gross total resection (GTR) was defined as Simpson 1-3. Recurrence was classified into early and late (≤ 24 vs. > 24 months).

Results: Among the 220 cases, 37 (16.8%) patients progressed within 24 months of operation. Independent predictors of early progression were subtotal resection (STR) (p = 0.005), parafalcine/parasagittal location (p = 0.015), peritumoural oedema (p = 0.027) and mitotic index (MI) > 7 (p = 0.007). Adjuvant radiotherapy was negatively associated with early recurrence (p = 0.046). Thirty-two per cent of patients with residual tumour and 26% after GTR received adjuvant radiotherapy. There was a significantly lower proportion of favourable outcomes at last follow-up (mRS 0-1) in patients with early recurrence (p = 0.001).

Conclusions: Atypical meningiomas are a heterogeneous group of tumours with 16.8% patients having recurrence within 24 months of surgery. Residual tumour, parafalcine/parasagittal location, peritumoural oedema and a MI > 7 were all independently associated with early recurrence. As administration of adjuvant radiotherapy was not protocolised in this cohort, any conclusions about benefits of irradiation of WHO grade II meningiomas should be viewed with caution. Patients with early recurrence had worse neurological outcome. While histological and imaging characteristics provide some prognostic value, further molecular characterisation of atypical meningiomas is warranted to aid clinical decision making.

Keywords: Atypical meningioma; Early progression; Early recurrence; Predictors of recurrence.

Fig. 1

Examples of radiological characteristics used in the study. a Peritumoural oedema manifested as T2 hyperintensity immediately surrounding the tumour with mass effect. b Irregular margins with ‘mushrooming’ and nodules appearing as if detached from main mass of tumour. c Bone involvement in a parasagittal meningioma. d Sinus involvement manifest with tumour clearly present in the cavity of the superior sagittal sinus

Fig. 2

Kaplan-Meier plots demonstrating a significant association between extent of resection; the use of adjuvant XRT; location (divided into convexity, parafalcine/parasagittal and skull base); peritumoural oedema and progression-free survival for patients with atypical meningiomas. Log rank test for significance used to determine statistical significance

Fig. 3

Kaplan-Meier plots demonstrating a significant association between presence of atypia; MI; MIB1 count and progression-free survival. MI has been dichotomised to MI ≤ 7/10 HPF and MI > 7/10 HPF and MIB1 has been dichotomised to MIB1 ≤ 15% and MIB1 > 15%. Log rank test for significance used to determine statistical significance

Fig. 4

Bar chart demonstrating the difference in clinical outcomes between the ‘early progression/recurrence’ groups. All others (top graph); below the same analysis is repeated excluding patient who never had a recurrence (bottom graph). Dashed line depicts differences in number of patients with favourable outcomes defined as mRS 0–1 at last follow-up. mRS-modified Rankin Scale