PTGS2 and nasopharyngeal carcinoma: Subgroup analysis by assay and staging criteria also provided evidence for an association between COX-2 and lymph node metastasis in NPC patients (ORIHC-SP = 6.29, 95%CI = 4.55–8.67; ORIHC-SABC = 2.42, 95%CI = 1.45–4.02)(Table 4).