Predictive Evolution Factors of Incidentally Discovered Suspected Low-Grade Gliomas: Results From a Consecutive Series of 101 Patients

BACKGROUND: Incidentally discovered suspected diffuse low-grade gliomas (LGGs) on brain imaging pose a challenge to neurosurgeons. Modern surgical series of LGGs favor early prophylactic surgery with a maximal extent of resection. However, some nonevo-lutive lesions may mimic LGGs on magnetic resonance imaging (MRI). OBJECTIVE: To determine objective criteria to advocate surgical resection of an incidentally discovered suspected LGG based upon MRI findings. METHODS: The prospective cohort of patients referred to our institution for an incidental finding suggestive of LGG was retrospectively reviewed. Stable lesions underwent systematic serial MRI follow-up, while evolutive lesions underwent prophylactic surgery under awake conditions. Initial clinico-radiological features were compared between stable and evolutive lesions in order to determine predictive criteria of further evolution. RESULTS: Among 101 patients referred for surgical resection of incidentally discovered suspected LGG in our center, 19 patients (18.8%) had nonevolutive MRI lesions after a mean follow-up of 46.9 +/- 34.9 mo. Insular topography (P = .003), higher mean volume at discovery (19.2 vs 5.2 cm(3), P < .001), and adjacent sulcal effacement (P = .001) were associated with evolutive lesions. Histopathological diagnosis of LGG was confirmed in all surgical cases. CONCLUSION: Increasing volume is an effective predictor of LGG diagnosis in incidental MRI findings, as all patients who subsequently underwent surgery had confirmed histopathological diagnosis of diffuse glioma. Approximately 18.8% of incidental findings were stable over time. Insular topography, adjacent sulcal effacement, and volume greater than 4.5 cm(3) were predictive of further radiological progression. These significant elements will help neurosurgeons to define personalized strategies in this complex setting of incidental discovery.