Treatment decision making based on the published natural history and growth rate of small meningiomas

Object. Definitive data allowing clinicians to predict which meningioma patients will fail to respond to conservative management are lacking. To address this need, the authors systematically reviewed the published literature regarding the natural history of small, untreated meningiomas. Methods. The authors performed a systematic review of the existing literature on untreated meningiomas that were followed with serial MR imaging. They summarize the published linear rates of tumor growth, and the risk factors for development of new or worsened symptoms during follow-up by using a stratified chi-square test. Results. The search methods identified 22 published studies reporting on 675 patients with untreated meningiomas followed by serial MR imaging. Linear growth rates varied significantly: no growth was the most common rate, although reports of more aggressive tumors noted growth rates of up to a 93% linear increase in size per year. The authors found that few patients with initial tumor diameters < 2 cm went on to develop new or worsened symptoms over a median follow-up period of 4.6 years. Patients with initial tumor diameters of 2-2.5 cm demonstrated a marked difference in the rate of symptom progression if their tumors grew > 10% per year, compared with those tumors growing ≤ 10% per year (42% vs 0%; p < 0.001, chi-square test). Patients with tumors between > 2.5 and 3 cm in initial size went on to develop new or worsened symptoms 17% of the time. Conclusions. This systematic review of the literature regarding the clinical behavior of untreated meningiomas suggests that most meningiomas ≤ 2.5 cm in diameter do not proceed to cause symptoms in the approximately 5-year period following their discovery. Those that do cause symptoms can usually be predicted with close radiographic follow-up. Based on these findings, the authors suggest the importance of observation in the early course of treatment for small asymptomatic meningiomas, especially those with an initial diameter < 2 cm.