The subventricular zone represents a niche of adult neural stem cells. Involvement of the subventricular zone is associated with decreased survival in malignant glioma. We aimed to determine whether a similar association applies to low-grade gliomas.
A retrospective institutional database search was performed for patients with glioma WHO grade II according to the 2016 classification. Demographic data, histology and molecular signature, imaging, and therapy were recorded and outcome was analysed for tumors with and without infiltration of the subventricular zone.
182 patients with glioma WHO grade II were identified, including 97 oligodendrogliomas and 85 astrocytomas. 78 of 182 patients (43%) presented with subventricular zone involvement. Demographics, histopathology, and molecular signature did not differ between patients with and without subventricular zone involvement. First-line management included surgery, chemotherapy, radiotherapy, brachytherapy, and wait-and-scan approaches. Median follow-up was 43 months. Median time to malignant progression was 122 months; median overall survival was not reached. Subventricular zone involvement was a negative prognostic marker for time to malignant progression (p = 0.002) and overall survival (p = 0.023) in the entire cohort as well as in the subgroup of patients who were managed with wait-and-scan approaches. Among patients in which early therapy was provided, subventricular zone involvement was not prognostic for overall survival but for time to malignant progression. In multivariate analysis, subventricular zone involvement was associated with worse prognosis independent of molecular markers or treatment approaches including use of resection.
Subventricular zone involvement represents a key risk factor for worse outcome in glioma WHO grade II. Early first-line therapy may improve outcome in such patients.