Impact of Multifocality and Molecular Markers on Survival of Glioblastoma

Several parameters like extent of resection and MGMT promotor methylation in glioblastoma (GBM) are known to influence survival. Other elements like multifocality and proliferation indices are not commonly used. The aim of the present study was to analyze routinely and not routinely assessed prognostic markers for survival of patients suffering from GBM in a single center.

Adult cases with GBM operated at our institution were included in this survey. The association of age, Karnofsky performance status (KPS), MGMT promotor methylation, Ki67 proliferation index, IDH1/2 mutational status, and multifocality on overall survival (OS) was analyzed in univariate and multivariate cox regression models.

We analyzed 565 patients with a mean age of 62.2 (18-84) years. Median OS was 12.5 months. MGMT promoter methylation and IDH 1/2 mutation were associated with significant better OS (P < 0.01). In 48 cases (8.5%), the tumor was localized in both hemispheres, which was associated with a significant worse OS than tumor infiltration of 1 hemisphere (P = 0.039). Mean Ki67 proliferation index increased to 18% when both hemispheres were infiltrated. Multivariate analysis for OS revealed IDH 1/2 wildtype (adjusted odds ratio [aOR] 4.3), higher age (aOR 4.2), unmethylated MGMT promotor (aOR 3.5), preoperative KPS score <70 (aOR 1.9), and multifocality (aOR 2.1) as independent parameters for worse survival.

This study confirms well-known parameters like MGMT promoter methylation, IDH 1/2 mutational status, KPS, and age as independent prognostic factors for survival and reveals multifocality as further independent prognostic marker for survival. The dismal prognosis of multifocal involvement is associated with an increasing Ki67 proliferation index.