IDO1 and nasopharyngeal carcinoma: First, the univariate analysis confirmed that IDO1 and IDO2 mRNA expression were significantly associated in NPC patients (p = .001; OR [95% CI] = 11.54 [2.87–46.40]) and this association was independent as shown by the multivariate analysis (p = .002; OR [95% CI] = 12.30 [2.57–58.94]).