To confirm these results, we performed a multivariate Cox proportional hazards analysis and found that TP53 status was significant in the IDH1 hotspot mutation subgroup (HR = 2.079; 95% CI: 1.083–3.992; p = 0.028), in the oligodendroglioma subgroup (HR = 2.001; 95% CI: 1.032–3.879; p = 0.040) (Table 6 and Table 7), as well as in the entire cohort (HR = 1.809; 95% CI: 1.327–3.150; p = 0.001) and the IDH1-wildtype subgroup (HR = 2.572; 95% CI: 1.378–4.802; p = 0.003) (Tables S7 and S8). This evidence concerns the gene TP53 and oligodendroglioma.