Polysomy of chromosomes 1 and 19: an underestimated prognostic factor in oligodendroglial tumors

The clinical significance of chromosomes 1 and 19 deletion was well established in oligodendroglial tumors (ODGs). This study was designed to evaluate the prognostic implication of chromosomes 1 and 19 polysomy in gliomas. 584 patients with histological diagnosis of primary gliomas enrolled in the study. Chromosomes 1 and 19 status was detected with fluorescence in situ hybridization (FISH). Of the 584 cases, the frequency of 1q and 19p polysomy in mixed gliomas was significantly higher than ODGs or astrocytic tumors (1q P = 0.032 and P = 0.044; 19p P = 0.024 and P = 0.027); the frequency of 1q and 19p polysomy in low-grade gliomas (WHO II) was relatively lower compared with WHO III or WHO IV (1q P = 0.097 and P = 0.026; 19p P = 0.04 and P = 0.002). 1q, 19p and co-polysomy were confirmed as risk factors conveyed unfavorable outcomes, which has been further validated in both anaplastic oligodendroglial tumors (AOGs) (P = 0.07, P = 0.028 and P = 0.054 for PFS; P = 0.007, P = 0.001 and P = 0.002 for OS, respectively) and glioblastomas with oligodendroglioma component (GBMOs) (P = 0.005, P < 0.001 and P < 0.001 for PFS; P = 0.136, P = 0.006 and P = 0.051 for OS, respectively). Based on chromosomes 1/19 co-deletion and co-polysomy, AOGs and GBMOs could be divided into three subgroups which harbored distinct prognosis (AOGs P < 0.001 for PFS and P < 0.001 for OS; GBMOs P < 0.001 for PFS and P = 0.012 for OS). Chromosomes 1/19 polysomy are potential prognostic factors which confer unfavorable outcomes. The molecular prognostic grouping model based on chromosomes 1/19 co-polysomy and co-deletion better predicts prognosis and provides a more reliable information for treatment decision-making.