The natural history of incidental meningiomas.

OBJECTIVE: Little information about the natural history of incidental meningiomas exists in the literature. The aim of this study was to determine the natural history of asymptomatic meningiomas by comparing different methods of growth rate calculation to establish a strategy for dealing with these tumors.

METHODS: In 47 asymptomatic patients, hospital charts, follow-up records, and imaging studies were reviewed. Of these patients, 6 underwent surgery. Tumor growth rates were determined by calculating the absolute and relative growth rates and the tumor volume doubling times.

RESULTS: In 41 patients with conservative management, the average tumor size was 9 cm(3), and the majority (66%) of growth rates were less than 1 cm(3)/yr. The absolute growth rate ranged from 0.03 to 2.62 cm(3)/yr (mean, 0.796 cm(3)/yr). Relative annual growth rates ranged from 0.48 to 72.8% (mean, 14.6%). The tumor doubling time ranged from 1.27 to 143.5 years (mean, 21.6 yr). A moderate correlation between the age and growth rates was found. In young patients, annual growth rates tended to be higher and tumor doubling times shorter. There was no clear correlation between the initial tumor size and tumor doubling time. The mean annual growth rate of meningiomas with calcification was lower than in tumors without calcification. Also, tumors with hypointense or isointense T2 signals on magnetic resonance imaging had a lower growth rate. In the group of six patients with surgical excision, tumor growth rates were higher and tumor doubling times shorter than in the nonsurgical group.

CONCLUSION: The majority of incidental meningiomas show minimal growth; thus, they may be observed without surgical intervention unless specific symptoms appear. Tumor growth is associated with patient age. The initial tumor size is not considered a predictive factor for tumor growth. Radiological features, such as calcification or T2 signal intensity, may provide useful information to predict the growth potential of meningiomas.