Serum concentrations of l-kynurenine predict clinical outcomes of patients with peripheral T-cell lymphoma, not otherwise specified

Indoleamine 2,3-dioxygenase exerts intense immunomodulatory effects due to enzymatic activities that catalyze the breakdown of the essential amino acid l-tryptophan. The activity of indoleamine 2,3-dioxygenase can be estimated by measuring serum l-kynurenine concentrations. Here, we aimed to determine the role of l-kynurenine as a prognostic factor for peripheral T-cell lymphoma, not otherwise specified (PTCL-NOS) in a retrospective analysis of data derived from 31 consecutive patients between June 2000 and March 2013 who were histologically diagnosed with PTCL-NOS according to the World Health Organization classification and treated with 6−8 cycles of cyclophosphamide, doxorubicin or pirarubicin, vincristine, and prednisolone. l-kynurenine concentrations in serum samples collected at admission were measured using high-performance liquid chromatography. The median serum concentration of l-kynurenine was 3.28 (range 0.92–8.16) μM. The l-kynurenine cutoff was set at 3.07 μM using receiver operating characteristics curves. The complete remission rates of patients with l-kynurenine <3.07 and ≥3.07 μM were 69% and 51%, respectively. The 5-year overall survival (OS) rates for patients with l-kynurenine <3.07 and ≥3.07 μM were 80.2% and 23.4%, respectively (p < 0.001). More advanced age, poor performance status, elevated lactate dehydrogenase, an unfavorable International Prognostic Index, and a poor prognostic index for T-cell lymphoma were significantly worse factors for OS. Multivariate analyses revealed only l-kynurenine as an independent prognostic factor for OS. In conclusion, serum concentrations of l-kynurenine might comprise a novel prognostic factor with which to determine the outcomes of treatment for PTCL-NOS.