Recurrence of spinal meningiomas: analysis of the risk factors

Objective: Spinal meningiomas are slow-growing tumors with low recurrence rate after complete resection. The aim of this study is to investigate the risk factors correlated to the recurrence. Material and Methods: Six patients with spinal WHO grade I meningiomas which recurred after complete resection were reviewed and compared to 50 patients with no recurrence; the data were also compared with those of 50 intracranial meningiomas which recurred and 50 which did not recur after complete resection. The investigated factors included age and sex, tumor location and size, type of arachnoid interface, entity of resection (Simpson I or II), tumor consistency and vascularity, histological type, Ki-67 MIB-1, progesterone receptor (PR) and estrogen receptor (ER) expression. The data were statistically analyzed with the Kaplan-Meier method. Results: The statistical analysis showed that the presence of arachnoidal invasion (p = 0.023) and higher Ki-67 LI (p < 0.0001) were the only two significant risk factors for recurrence for both spinal and intracranial meningiomas. Large tumor size (p = 0.012), Simpson grade II resection (p = 0.03) and the absence of PR expression (p < 0.0001) were significant risk factors for recurrence of intracranial but not spinal meningiomas. Finally, age and sex, tumor location, consistency and vascularity, histological type, and ER expression were not correlated to recurrence for both localizations. Conclusions: The proliferation index Ki-67 and the arachnoid invasion are the risk factors for recurrence of spinal meningiomas, whereas tumor size, dural resection and PR expression are not significant. The small tumor size and the limited dural invasion may contribute to explain the lower recurrence rate.