PTGER4 and neoplasm: The results of the Kaplan–Meier analysis of 5-year RFS, PFS, and OS indicated significant differences between the groups with versus without hypermethylation at the CpG_4.5, CpG_15, and CpG_17 sites of tumor tissue that underwent PTGER4 methylation (p = 0.002 for RFS, 0.001 for PFS, and <0.001 for OS; Figure 2).