Extent of Resection Is Potent Prognostic Factor Next to Molecular Pathologic Subtype in Low-Grade Glioma

Abstract

The optimal treatment of low-grade glioma (LGG) remains one of the most controversial areas in neuro-oncology. We aimed to evaluate treatment outcomes and identify prognostic factors of LGG patients according to the new 2016 WHO classification. The record of 137 patients diagnosed as WHO grade II LGG between March 2003 and February 2014 were retrospectively reviewed. Based on the 2016 WHO classification, 69 patients (50.4%) had diffuse astrocytoma (DA), IDH mutant; 44 patients (32.1%) had oligodendroglioma (ODG), IDH mutant and 1p/19q codeleted; and 24 patients (17.5%) had DA, IDH wild-type. The median age at diagnosis was 41 years (range, 22-74). Gross total resection (GTR) was performed in 66 patients (48.2%), subtotal resection in 34 (24.8%), partial resection in 27 patients (19.7%), and biopsy in 10 patients (7.3%). Eighty-seven patients (63.5%) received postoperative radiotherapy (RT). The median follow-up time was 71.1 months (range, 5.3-170.9). The 5-year and 10-year progression free survival (PFS) were 70.3% and 52.3%, and 5-year and 10-year overall survival (OS) were 82.9% and 63.7%, respectively. GTR and molecular subtype of IDH mutant and/or 1p/19q codeletion were favorable prognostic factors for both PFS and OS. Patients with tumoral IDH wild-type had significantly decreased OS than those with IDH mutation and 1p/19q codeletion. Among patients with ODG underwent GTR, no failure was observed after RT. Patients with IDH mutant and wild-type performed non-GTR had high recurrent rates after RT (51.7% and 62.5%). Regarding OS, age (<40 years), tumor size (<6cm), tumor location (frontal lobe), chemotherapy, and RT were not significant prognostic factors on multivariate analysis. Molecular classification in LGG was of prognostic relevance, with the tumors that do not have IDH mutations and/or 1p/19 codeletion having a particularly poor outcome regardless of treatment. The favorable results were observed in patients who undergone GTR. Prospective study is needed to demonstrate the role of adjuvant treatment in LGG.