The IMPACT Tool Helps Guide Management of Incidental Meningiomas

By Rajiv S. Magge, MD

Synopsis: In a large international, multicenter, retrospective cohort, the imaging-based IMPACT tool accurately predicted progression risk of incidental meningiomas and effectively stratified patients into low-, medium-, and high-risk groups at initial diagnosis.

Source: Islim AI, Millward CP, Zakaria R, et al; IMPACT Study Investigators, International Consortium on Meningioma (ICOM) and British Neurosurgical Trainee Research Collaborative (BNTRC). A clinical tool to identify incidental meningioma for early outpatient management. JAMA Oncol. 2025; Nov 20. doi: 10.1001/jamaoncol.2025.4821. [Online ahead of print].

Meningiomas are dural-based extra-axial masses and among the most common primary central nervous system (CNS) tumors. Although most are benign (World Health Organization [WHO] grade 1), they can grow at variable rates and cause significant morbidity, especially when associated with mass effect or proximity to eloquent brain and critical neurovascular structures.

Many meningiomas are diagnosed incidentally on imaging obtained for other neurologic symptoms, such as headache or dizziness. Definitive treatment with surgical resection typically is recommended for large and/or symptomatic tumors, especially when accompanied by parenchymal edema, hemorrhage, necrosis, or signs of infiltration.

Small, asymptomatic tumors often are monitored with surveillance imaging; many will never require surgery or radiation therapy (RT), although further growth eventually may contribute to neurologic morbidity. Historically, we have lacked effective tools to predict which tumors will progress and cause dysfunction — criteria to intervene often include growth rate and symptom development but remain ill-defined. Moreover, slow growth may be clinically inconsequential, and patients with poor functional status or significant comorbidities may be more likely to die of other illnesses.

In this retrospective cohort study spanning 33 centers in 15 countries, Islim et al externally validated their previously developed Incidental Meningioma: Prognostic Analysis Using Patient Comorbidity and MRI Tool (IMPACT) for predicting the risk of incidental meningioma progression and need for intervention. The IMPACT tool first estimates progression risk using T2-weighted magnetic resonance imaging (MRI) tumor hyperintensity, peritumoral edema, and proximity to critical neurovascular structures, then incorporates comorbidity burden and functional status to weigh that risk against the competing risk of death from other causes.

Adults with newly diagnosed incidental meningioma between January 2009 and December 2010 were included and followed until intervention, death, or last clinical encounter. The primary outcome was a composite endpoint comprising growth, symptom development, meningioma-related mortality, and imaging features indicating loss of a curative window (peritumoral edema, venous sinus invasion, or tumor volume > 10 cm³). Secondary endpoints were subsequent intervention and non-meningioma-related mortality. IMPACT scores were calculated and categorized as low-, medium-, or high-risk. Performance was assessed with standard discrimination and calibration metrics.

Overall, 1,248 patients with incidental meningioma were included. The most common scan indications were headache and audiovestibular symptoms. Nearly one-quarter of patients received upfront treatment, predominantly surgical resection. Although some patients lacked longitudinal imaging and were lost to follow-up, the treatment-naive group was followed a median of 61 months: 12% progressed, 13.1% underwent an intervention, and 40.5% died without progression or intervention from non-meningioma causes. Five- and 10-year progression-free survival (PFS) rates were 88.1% and 85.7%, respectively, indicating that most patients do well without significant tumor growth.

Patient stratification with the IMPACT score also was clinically meaningful: Low-, medium-, and high-risk groups had progression risks of 3.9%, 24.2%, and 51.6%, respectively. Discrimination and overall performance (analyses included Brier score, C-statistic, and time-dependent area under the curve to 10 years) supported the tool’s predictive accuracy. Importantly, when combined with the Age-Adjusted Charlson Comorbidity Index (ACCI) and WHO performance status (PS), the model identified patients more likely to die of other causes than to require meningioma-directed intervention after diagnosis.

Commentary

This impressive study shows that the IMPACT tool performs well across a large, multicenter, retrospective cohort. Beyond risk prediction, each patient’s IMPACT category can pragmatically guide management, supporting early intervention for high-risk tumors, serial monitoring for medium-risk tumors, and extended monitoring or safe discharge for low-risk tumors.

Epigenetic testing has transformed meningioma classification (and often outperforms WHO grade for identifying aggressive biology), but the unique advantage of IMPACT is that it is preoperative and noninvasive, assigning high, medium, or low risk without tissue. Incorporating ACCI and PS is equally valuable, distinguishing patients with high comorbidity or poor performance status who are more likely to die of other causes than ever need treatment of their meningioma. By showing that low-risk lesions rarely progress (and that most recur within five years when they do) and that some sicker patients will not live to need intervention, the tool may help conserve resources and avoid unnecessary follow-up.

As with all retrospective multi-institutional studies, limitations of the study included non-standardized management across sites, imaging and technical variability, and lack of central imaging review. Rating edema, necrosis, hemorrhage, or brain invasion on MRI — especially in a binary fashion — can be quite challenging. In addition, the utility of tumor T2 hyperintensity as a predictor of growth has not been uniformly reproducible in prior meningioma imaging studies. The quarter of patients who received upfront treatment were younger, had fewer comorbidities, and had larger tumors, so the remaining 75% under observation may have been less likely to progress (contributing to slight overprediction in higher-risk tiers).

These caveats reinforce the need for prospective implementation study of the IMPACT tool with central imaging review, harmonized imaging protocols, and standardized management (which admittedly could be difficult in a largely indolent disease). The first question most patients with incidental meningioma ask is whether their tumor will grow or require treatment. The IMPACT tool allows a more precise, evidence-based answer.

Rajiv S. Magge, MD, is Associate Professor of Clinical Neurology, Weill Cornell Medicine, Weill Cornell Brain Tumor Center.