The Simpson grading revisited: aggressive surgery and its place in modern meningioma management

From 1953 to 1980, 657 patients survived a seemingly complete removal of a histologically benign intracranial meningioma. Recurrence of the tumor was found in 59 of these 657 patients, but some cases of recurrence may have been missed inasmuch as only 69 patients were followed for 20 years. With ordinary life-table analysis, the overall recurrence rate was estimated to be 19% at 20 years. The reliability of this result was evaluated with a modified life-table analysis. Multivariate analysis showed that coagulation of the dural insertion, invasion of bone, and soft consistency of tumor were strong risk factors (p less than 0.01) for recurrence. The recurrence rate at 20 years was estimated to be 11% for the 249 patients with none of these risk factors, 15-24% for those with one factor, and 34-56% for those with two.

Techniques for the surgical treatment of meningioma have undergone many improvements since Simpson established the neurosurgical dogma for meningioma surgery in his seminal paper published in 1957. This study aims to assess the clinical significance and limitations of the Simpson grading system in relation to modern surgery for WHO Grade I benign meningiomas and to explore the potential of the cell proliferation index to complement the limitations in predicting their recurrence. The surgical records of patients who underwent resection of intracranial meningiomas at the University of Tokyo Hospital between January 1995 and August 2010 were retrospectively analyzed. The authors investigated the relationships between recurrence-free survival (RFS) and Simpson grade or MIB-1 labeling index value. A total of 240 patients harboring 248 benign meningiomas were included in this study. Simpson Grade IV resection was associated with a significantly shorter RFS than Simpson Grade I, II, or III resection (p<0.001), while no statistically significant difference was noted in RFS between Simpson Grades I, II, and III. Among meningiomas treated by Simpson Grade II and III resections, however, multivariate analysis revealed that an MIB-1 index of 3% or higher was associated with a significantly shorter time to recurrence. The clinical significance of the different management strategies related to Simpson Grade I-III resection may have been diluted in the modern surgical era. The MIB-1 index can differentiate tumors with a high risk of recurrence, which could be beneficial for planning tailored optimal follow-up strategies. The results of this study appear to provide a significant backing for the recent shift in meningioma surgery from attempting aggressive resection to valuing the quality of the patient's life.