With the use of median value as cutoff, patients with kyn/trp ratio > 0.06 had a higher risk to develop an early progression (within 3 months) to nivolumab with a trend toward significance ( p = 0.064 at multivariate analysis).
Indeed, the pathway is responsive to unspecific inflammation, and it is induced in chronic immune activation states because IDO is sensitive IFN gamma gene, and it is induced by inflammatory stimuli ( 27 ) that may be significant especially in locally relapsed HNSCC, which is generally an inflamed disease.