55PTryptophan catabolism differentiates breast cancer patients from healthy controls but does not predict outcome

Background: Indoleamine 2,3 dioxygenase (IDO) catalyzes the conversion of tryptophan (Trp) into kynurenine (Kyn), an immunosuppressive metabolite involved in T regulatory cell differentiation. IDO is expressed in many cancer types, including breast cancer (BC), but its association with prognosis is controversial. Here we analyze Kyn/Trp ratio, known as a surrogate indicator of IDO activity, in BC patients and in healthy control (CTRL).