Proliferation potential of spinal meningiomas

The goal of the present study was to quantitatively assess the proliferation index and progesterone receptor status of spinal versus intracranial meningiomas and to determine if these biological indicators can describe the clinical behavior of these tumors. This information could provide the spinal surgeon with important additional information concerning surgical management and follow-up recommendations for the individual patient.

The study group consisted of 26 patients with spinal and 241 patients with intracranial meningiomas. Patients with atypical or anaplastic tumors as well as with neurofibromatosis type II were excluded from the study. Furthermore both groups were matched according to age, sex and resection grade (total resection according the Simpson classification). Proliferation index (Ki-67 Labelling index [LI]) and progesterone-receptor (PR) status of spinal and intracranial meningiomas were compared. Clinical charts including surgical and histological records and imaging studies were reviewed. Correlations with histological subtype, intratumoral calcifications, tumor vascularity and recurrence-free survival were analyzed.

Compared to the spinal group with a mean Ki-67 LI of 2.48% and a positive PR-status of 46%, proliferation rates of intracranial meningiomas were significant higher (Ki-67 LI 3.6%; P-value 0.041). No significant difference in PR status was seen (spinal PR-status 46%, P-value 0.261). Furthermore spinal meningiomas were less vascularized and showed less intratumoral calcifications. Time to recurrence was similar in spinal and intracranial tumors.

Spinal and intracranial meningiomas differ in their proliferation activity but not in their PR status. However, despite lower proliferation rates, time to recurrence in spinal and cranial meningiomas is comparable in totally excised tumors. Further studies are needed to determine the role of other biological indicators in spinal meningioma growth and response to therapy.