Slower growth of skull base meningiomas compared with non–skull base meningiomas based on volumetric and biological studies

Abstract

Object The precise natural history of incidentally discovered meningiomas (IDMs) remains unknown. It has been reported that for symptomatic meningiomas, tumor location can be used to predict growth. As to whether the same is true for IDMs has not been reported. This study aims to answer this question and provide biological evidence for this assumption by extending the study to involve symptomatic cases. Methods A total of 113 IDMs were analyzed by fine volumetry. A comparison of growth rates and patterns between skull base and non–skull base IDMs was made. Subsequently, materials obtained from 210 patients with symptomatic meningiomas who were treated in the authors' hospital during the same period were included for a biological comparison between skull base and non–skull base tumors using the MIB-1 index. Results The 110 patients with IDMs included 93 females and 17 males, with a mean follow-up period of 46.9 months. There were 38 skull base (34%) and 75 non–skull base (66%) meningiomas. Forty-two (37%) did not exhibit growth of more than 15% of the volume, whereas 71 (63%) showed growth. Only 15 (39.5%) of 38 skull base meningiomas showed growth, whereas 56 (74.7%) of 75 non–skull base meningiomas showed growth (p = 0.0004). In the 71 IDMs (15 skull base and 56 non–skull base), there was no statistical difference between the 2 groups in terms of mean age, sex, follow-up period, or initial tumor volume. However, the percentage of growth (p = 0.002) was significantly lower and the doubling time (p = 0.008) was significantly higher in the skull base than in the non–skull base tumor group. In subsequently analyzed materials from 94 skull base and 116 non–skull base symptomatic meningiomas, the mean MIB-1 index for skull base tumors was markedly low (2.09%), compared with that for non–skull base tumors (2.74%; p = 0.013). Conclusions Skull base IDMs tend not to grow, which is different from non–skull base tumors. Even when IDMs grow, the rate of growth is significantly lower than that of non–skull base tumors. The same conclusion with regard to biological behavior was confirmed in symptomatic cases based on MIB-1 index analyses. The authors' findings may impact the understanding of the natural history of IDMs, as well as strategies for management and treatment of IDMs and symptomatic meningiomas.

Clinical features and surgical management of intracranial meningiomas in the elderly

“…The growth rate of intracranial meningiomas has been reported as 2.4-5.3 mm per year (27)(28)(29). Other studies have reported that hyperintensity on T2-weighted imaging, a non-skull base location and the absence of calcification on imaging are considered positive indicators of tumor growth in intracranial meningiomas (30,31). In addition, a non-skull base location and the absence of calcification correlate with a high tumor proliferation index (MIB-1) in intracranial meningiomas (32)(33)(34)(35).…”

“…However, the risk of surgical treatment must be balanced against the morbidity due to tumor growth that is associated with a conservative treatment. Previous studies have investigated the natural history of intracranial meningiomas (26)(27)(28)(29)(30). The growth rate of intracranial meningiomas has been reported as 2.4-5.3 mm per year (27)(28)(29).…”

Reliability of the Size Evaluation Method for Meningiomas: Maximum Diameter, ABC/2 Formula, and Planimetry Method

“…The planimetry method has been widely used to calculate the volume of meningiomas in previous studies (3,4,(11)(12)(13)(14)(15); however, the details of the procedure depend on each investigator. The thickness of MRI used in the planimetry method is often not regarded in the study.…”

“…Although some studies have used the ABC/2 formula (2,25,26) or the original ellipsoid volume (10,19,27) to measure the volume of intracranial tumors, including meningiomas, few studies have evaluated the accuracy of ABC/2 formula for intracranial tumors. The planimetry method presents a more approximate volume for the real tumor and has been applied in many studies (3,4,(11)(12)(13)(14)(15); however, this method is more cumbersome than the ABC/2 method. In addition, the thickness of MRI used to calculate tumor volume differs between each investigator.…”

The Natural Course of Incidental Intracranial Meningiomas: Systematic Review and Meta-Analysis.

“…Published reports are often limited by a retrospective study design, small sample size, and short follow-up period. [1][2][3][4][5][6][7][8][9][10][11][12][13][14]16,17,19,[21][22][23] A systematic review and meta-analysis of the studies currently available allows for a better understanding of the natural course of asymptomatic meningiomas, a platform for more research, and a foundation on which a standardized guideline for following these tumors may be built.…”