To determine, in our patient cohort (n = 71), whether IDO-positivity in the PT microenvironment correlates with serum levels of IDO metabolites tryptophan, kynurenine, and 3-hydroxykynurenine, we used previously measured serum levels from a cohort of 251 cervical cancer patients where a high kyn/trp ratio was shown to be detrimental for survival (32). This evidence concerns the gene IDO1 and cervical cancer.