IDO1 and cancer: To further investigate associations between IDO1 and immune factors, odds ratios for high IDO1 expression based on selected immune markers (high vs. intermediate/low), microsatellite instability (high vs. stable), tumor mutational burden (TMB) (high vs. low, using 10 or 20 mutations/mb as cutoff), and cancer types were calculated and compared using univariate and multivariate analyses (Table 1).