Frequency and Prognostic Impact of CDKN2A/B Alteration in Oligodendrogliomas: Systematic Review and Meta-analysis.

Isocitrate dehydrogenase (IDH) -mutant astrocytomas with homozygous deletion of cyclin-dependent kinase 2A/B (CDKN2A/B-HomoD) are categorized to grade 4 in the new World Health Organization (WHO) classification. However, the clinical implications of CDKN2A/B-HomoD in oligodendrogliomas remain unclear. This study systematically reviewed and meta-analyzed the literature on molecularly defined oligodendrogliomas (mOlig) to find the frequency and prognostic significance of CDKN2A/B gene alterations. Overall survival was worse in patients with CDKN2A/B-HomoD [pooled hazard ratio (pHR) 2.44; 95% confidential interval (CI), 1.59-3.76; P < 0.0001; 7 studies, 1,012 patients] than in those without CDKN2A/B-HomoD. Although the frequency (95% CI) was very low in grade 2 tumors (0.31%; 0.02-0.4) than in grade 3 tumors (9.4%; 6.2-14.0; I