Intracranial Meningiomas: A Systematic Analysis of Prognostic Factors for Recurrence in a Large Single Institution Surgical Series

Background

Meningioma is the most common primary intracranial tumor. Surgical resection is the first choice of treatment, whereas the role of adjuvant radiotherapy (RT) is still unclear. Aim of the study was to evaluate prognostic factors influencing the local recurrence rate.

Methods

Patients who had grade I-II meningiomas and underwent surgery were included in the present study. The extent of surgical resection was defined according to Simpson criteria, and were dichotomized as gross total and subtotal resection (STR). Adjuvant RT was considered in case of STR. Clinical outcome was evaluated by neurological examination and brain magnetic resonance imaging, which was performed every 6 months for the first year and yearly thereafter.

Results

From January 2000 to December 2015, 296 patients were analyzed. Most were women (65.9%), with a Karnofsky performance status ≥80 (94.6%), grade I meningioma (79.4%), and symptoms at diagnosis (91.5%). STR was performed in 58%, followed by adjuvant RT in 10%. Improvement or stability of neurological status was obtained in 90.4% of patients. The median follow-up time was 79 months (range, 24–214 months). Local recurrence occurred in 87 (29.4%) patients, at a median time of 56 months (range, 6–214 months). No patients, who underwent surgery plus adjuvant RT, had local relapse. The median, 2-, 5-, 10-year progression-free survival were 172 months, 91.1%, 80.7%, and 67.2%, respectively. On univariate and multivariate analysis factors impacting on progression-free survival were grade, extent of surgical resection, and adjuvant RT in case of STR, regardless of meningioma grade.

Conclusions

Overall, our findings suggest that recurrence rates are influenced by grade, extent of surgical resection, and use of adjuvant RT in not completely resected meningioma, regardless of tumor grade.

Introduction

Meningioma is the most common primary intracranial tumor, accounting for 15%–30% of primary brain tumors. According to World Health Organization (WHO) classification, about 80% are benign slow-growing meningiomas defined as grade I, associated with a low risk of recurrence after resection (∼ 10% at 5 years), 20% are atypical grade II meningiomas characterized by an intermediate clinical behavior, with a recurrence rate of 30%–40%, and <5% are anaplastic, aggressive, grade III meningiomas with a recurrence rate of 50%–80%.1, 2, 3 As recently highlighted by the European association of neuro-oncology guidelines, surgical resection is the first choice of treatment and should aim to achieve Simpson grade I resection.⁴ The amount of surgical resection, as defined by Simpson criteria, represents a crucial factor influencing the risk of recurrence.⁵ In case of Simpson grade I-II the 5-year local control rate accounts for 88%–95% in case of WHO grade I meningiomas and 60%–80% in case of WHO grade II. Conversely, for Simpson grade III-IV, the rate of local control is 50% on average.6, 7, 8 Therefore, most tumors are in favorable locations (convexity meningiomas and easily accessible skull-base meningiomas) in patients with WHO grade I. These tumors can be cured by surgery alone. WHO grade II meningioma implies an increased risk of recurrence after surgery alone, and an adjuvant treatment should be considered. The role of adjuvant radiotherapy (RT) is still unclear, particularly regarding the optimal timing and fractionation. Retrospective series on adjuvant radiotherapy after gross total resection led to different results, and prospective data are missing.4, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27 In a recent retrospective case study of 45 patients with atypical meningioma, Endo et al²⁸ showed no additional benefit of adjuvant radiotherapy in terms of long-term tumor control. In contrast, Lee et al²⁹ described a partial improvement of progression-free survival (PFS) in patients with subtotal resection and adjuvant radiotherapy. The ROAM/EORTC 1308 trial (ISRCTN71502099) is recruiting patients with newly diagnosed atypical meningioma (WHO grade II) who have undergone resection (Simpson grade I–III) and will be randomly assigned to either early adjuvant radiotherapy (60 Gy in 30 fractions) or observation with the aim to investigate whether RT reduces or delays the risk of tumor recurrence.³⁰ At present, consolidate evidence about the optimal therapeutic strategy is lacking. Based on this background we systematically analyzed the outcome of a large cohort of patients with WHO grade I and II intracranial meningioma who were consecutively treated in our institution. In the present study we evaluated prognostic factors influencing the local recurrence rate, with the aim of suggesting the most adequate treatment.