Moreover, Kaplan–Meier analysis and multivariable cox regression revealed that FLI1-IDO1 level had a negative correlation with OS and locoregional recurrence-free survival times (Fig. 7D, E), establishing FLI1-IDO1 expression as an independent prognostic factor in NPC (Fig. 7F, G). This evidence concerns the gene IDO1 and nasopharyngeal carcinoma.