Volumetric growth rate of incidental asymptomatic meningiomas: a single-center prospective cohort study

Decision about treatment of incidentally found intracranial meningiomas is controversial and conditioned by the growth potential of these tumors. We aimed to evaluate the growth rate of a cohort of incidentally found asymptomatic meningiomas and to analyze their natural course and the need for eventual treatment.

A total of 193 patients harboring intracranial meningiomas (85 with 109 incidental and 108 with 112 symptomatic) were included between 2015 and 2019. In the prospective cohort of incidental meningiomas, we measured size at diagnosis, volumetric growth rate (by segmentation software), appearance of symptoms, and need for surgery or radiotherapy. Progression-free survival and risk factors for growth were assessed with Kaplan-Meier survival and Cox regression analyses.

Among incidental meningiomas, 94/109 (86.2%) remained untreated during a median follow-up of 49.3 months. Tumor growth was observed in 91 (83.5%) and > 15% growth in 40 (36.7%). Neurological symptoms developed in 1 patient (1.2%). Volume increased an average of 0.51 cm³/year (95% CI, 0.20-0.82). Nine patients were operated (9.2%) and 4 underwent radiotherapy (4.7%). Treatment-related complication rates of incidental and symptomatic meningiomas were 0% and 35.4%, respectively. Persistent neurological defects occurred in 46 (40.7%) of symptomatic versus 2 (2.3%) of incidental meningiomas. Among covariates, only brain edema resulted in an increased risk of significant tumor growth in the female subgroup (Cox regression HR 2.96, 95% CI 1.02-8.61, p = 0.046). Size at diagnosis was significantly greater in the symptomatic meningioma group (37.33 cm³ versus 4.74 cm³, p < 0.001).

Overall, 86% of incidentally found meningiomas remained untreated over the first 4 years of follow-up. The majority grew within the 20% range, yet very few developed symptoms. Treatment-related morbidity was absent in the incidental meningioma group.