Insular Low Grade Gliomas (LGG): The Role of Molecular Markers and Extent of Surgical Resection (EOR)
Giovanna De Maglio, Tamara Ius, Miran Skrap, Stefano Pizzolitto. University Hospital S.Maria della Misericordia, Udine, Italy
Background: Insular gliomas represent the 25% of all Low Grade Gliomas (LGG) and are a surgical challenge for anatomo-functional reasons. The achievement of a radical resection is limited by their attitude to infiltrate the eloquent cortical areas and functional subcortical pathways. The role of EOR of insular gliomas on overall survival (OS) has been recently demonstrated, while the impact of the molecular profile in these lesions has not been investigated up to now.
Design: A cohort of consecutive 34 patients, resected for insular LGG, were retrospectively investigated from a molecular and volumetric point of view. Formalin fixed and paraffin embedded tissues were analysed for p53, 1p19q deletion, IDH1/IDH2 gene status and MGMT promoter methylation. Histologic and grade evaluation were performed according to WHO classification. The EOR was computed by analyzing pre- and post-operative T2-weighted MRI images.
Results: Patients were histologically classified as follows: astrocytomas, oligodendrogliomas and mixed oligoastrocytomas in 58.8%, 11.8% and 29.4% of cases respectively. A positive immunohistochemistry expression of p53 was observed in 61.8% of cases, while IDH1 mutation was found in 85.3% of cases (R132H and R132G mutations). All cases were wild-type for IDH2. MGMT promoter resulted methylated in 73.5% of patients and 1p/19q codeletion was demonstrated in 35.3% of samples. The mean EOR was 85% (54-100). Histological subtype (p<0.001), EOR (p<0.002) and 1p/19q codeletion (p<0.014) were demonstrated to be associated with OS at univariate statistical analysis. EOR has been proved to be the strongest independent predictive factor of OS by multivariate analysis (p=0.048). In 12 patients a second surgery for tumoral progression has been performed. In these cases, the molecular profile was similar to that of patients without tumoral recurrence. However the absence of 1p/19q codeletion was associated to a higher risk of recurrence (p=0.02).
Conclusions: The present investigation strengthened the prognostic value of EOR on OS. Biomarkers expression confirmed literature data on LGG, suggesting that insular LGG are not characterized by a specific molecular profile. OS was not significantly influenced by molecular markers even though absence of 1p/19q codeletion has been proved to be more associated to the risk of tumor recurrence.
Wednesday, March 6, 2013 1:00 PM
Poster Session VI # 241, Wednesday Afternoon