PTGS2 and nasopharyngeal carcinoma: In the same manner, several other studies found a significant association between higher COX-2 level and reduced OS both in univariate and multivariate analyses, including studies on OPSCC [93], OSCC [94], LSCC [62], HNSCC [28,52], NPC [65,84], HPSCC [64], and glottic cancer [89].