A Clinical Tool to Identify Incidental Meningioma for Early Outpatient Management

Importance Incidental meningiomas are common. There is a need for a validated clinical tool to stratify patients into early intervention, serial monitoring, or safe discharge from outpatient care. Objective To externally validate the Incidental Meningioma: Prognostic Analysis Using Patient Comorbidity and Magnetic Resonance Imaging Tests (IMPACT) tool. Design, Setting, and Participants This retrospective cohort study included 33 centers in 15 countries. Adult patients diagnosed with an incidental meningioma from January 2009 to December 2010 were included, up to the point of intervention, death, or last clinical encounter. Patients with radiation-induced meningioma and NF2-related schwannomatosis were excluded. Data collection was completed on December 31, 2023. Statistical analysis was conducted between March 2024 and December 2024. Main Outcomes and Measures The primary outcome of the study was a composite end point comprising growth, symptom development, meningioma-related mortality, and end points related to loss of window of curability. Secondary end points included the occurrence of an intervention and nonmeningioma-related mortality. Results Overall, 1248 patients were included. The median (IQR) age was 66 (55-77) years and 999 were female individuals (80%). There were 945 patients (75.7%) who had 1010 treatment-naive meningiomas. During follow-up (median [IQR], 61 [17-108] months), 114 tumors (11.3%) in 113 patients (12%) progressed, 132 tumors (13.1%) in 126 patients (13.3%) underwent an intervention, and 383 patients (40.5%) died without progression or intervention, from a nonmeningioma-related cause. The 5- and 10-year progression-free survival rates were 88.1% (95% CI, 85.8%-90.5%) and 85.7% (95% CI, 83.2%-88.2%), respectively. A low-risk meningioma had a disease progression risk of 3.9%, compared with 24.2% in medium-risk meningioma, and 51.6% in high-risk meningioma (χ² test, P < .001). Measures of external validity were adequate (Brier score = 0.12; C-statistic = 0.80; 10-year area under the curve, 0.83) and the addition of other variables in a Cox regression analysis did not confound the statistical significance of the IMPACT tool. Patients with an age-adjusted Charlson Comorbidity Index score of 6 or higher (eg, a patient aged 80 years with type 2 diabetes and a previous myocardial infarction) and a performance status of 2 to 4 (unable to carry out any work activities or in a chair/bed for 50% or more of the day) were more likely to die of other causes than to receive intervention following diagnosis. Conclusions and Relevance This cohort study found that the IMPACT tool accurately predicted the risk of incidental meningioma progression and can be used to stratify patients into early intervention, serial monitoring, or safe discharge from outpatient care.