BACKGROUND This study aimed to evaluate the association between soluble TGF-β (sTGF-β) and soluble PD-L1 (sPDL1), the dynamics of sTGF-β during treatment and its prognostic role in biliary tract cancer (BTC).

METHODS The study population consisted of 90 BTC patients with first-line chemotherapy (cohort 1) and 35 BTC patients with second- or third-line chemotherapy (cohort 2). Plasma sTGF-β and sPDL1 levels were measured using an enzyme-linked immunosorbent assay.

RESULTS In both groups, sTGF-β was positive correlated with sPDL1 for baseline and change values after treatment. sTGF-β was elevated at disease progression compared to baseline in cohort 1 (P < .001). Increased sTGF-β after treatment revealed worse DFS and OS (P = .024, P = .028, respectively) in cohort 1 and significantly shorter OS (P = .020) in cohort 2. In multivariable analysis, this prognostic value of increased sTGF-β for OS retained its significance in both cohorts (Hazard ratio (HR) = 1.8, 95% CI, 1.1-3.0, P = .028, in cohort 1; HR = 4.7, 95% CI, 1.5-14.6, P = .007, in cohort 2).

CONCLUSIONS In BTC, sTGF-β was positively correlated with sPDL1 for baseline and changes after chemotherapy, and increased as tumour burden. sTGF-β could be associated with survival; particularly, an elevated value after treatment suggests worse prognosis.