LAUSR

OBJECTIVE Meningiomas are the most frequent primary brain tumors. However, the long-term natural history of asymptomatic meningiomas remains unclear and difficult to predict accurately. The purpose of this study was to determine the subsequent course of asymptomatic meningiomas preceded by five years of no treatment. METHODS We retrospectively studied patients with radiologically suspected intracranial asymptomatic meningiomas preceded by five years of no treatment. We volumetrically measured the lesions' chronological changes during the initial five years to obtain the 5-year tumor doubling time (5y-TdT). RESULTS Two hundred one cases met the inclusion criteria. They were further divided into three subgroups: those who remained asymptomatic as group A (174 cases), those who developed neurological symptoms and underwent treatment as group B (8 cases), and those who received intentional intervention for a preventative reason as group C (19 cases). 5y-TdT of group B (median 46.5 months) was significantly shorter than that of group A (median 216.3 months) (p < .001). Progression-free survival (PFS) was significantly different between tumors that exhibited 5y-TdT ≥98.8 months and <98.8 months (p < .001). When we combined group B and C and set the PFS endpoint as either disease progression or treatment, we found that more than 20% of patients would require treatment within 15 years. CONCLUSIONS The present study revealed the subsequent courses of asymptomatic meningiomas after five years of no treatment and demonstrated that 5y-TdT is useful to detect patients who may require treatment.