WHO grade 1 meningioma recurrence: Are location and Simpson grade still relevant?

OBJECTIVE: To examine whether Simpson grade and pathology location are still predictors of recurrence/progression free survival (RPFS) in WHO grade 1 cranial meningiomas.
METHODS: A retrospective case series of all WHO grade 1 cranial meningiomas undergoing surgical resection at our institution between 2002 to 2007 was performed. Demographic and outcome data included: Simpson grade, extent of resection [gross total (Simpson 1-3) and sub total (Simpson 4-5)], tumour location, timing of post-operative imaging and outpatient review, time to recurrence and subsequent management. Statistical analysis was by Kaplan-Meier survival curves.
RESULTS: 145 cases were included of which 75% were female, with an overall median age of 55 years. 24% had parasagittal, 23% convexity and 53% skull base meningioma. 21% had a grade 1 Simpson resection, 43% grade 2, 35% grade 4 and 1% grade 5. The median follow up period was 60 months with a median 5.5 outpatient appointments and 5 post-operative imaging studies. 10 cases (6.9%) had recurrence/progression at a median period of 42 months. Of these, 4 remained under active surveillance, 3 received stereotactic radiosurgery and 3 were treated with fractionated radiotherapy. 5 year recurrence/progression free survival (RPFS) for Simpson grade 1 was 96.8%, 2: 100%, 4: 82.4% and 5: 0%. Simpson grade (p=0.01) and gross total/sub total resection (p=0.001) were significant predictors of RPFS. Meningioma location was not a significant predictor of RPFS (p-value 0.836).
CONCLUSION: Simpson grade remains a significant predictor of RPFS in WHO grade 1 meningioma surgery. However, tumour location was not significant in this series. We advocate different post-operative imaging surveillance protocols depending on gross total or sub total surgical resection.