Study design and patient characteristics

This observational cohort study was performed to analyze circulating levels of suPAR and their potential diagnostic and/or prognostic role in patients with BTC undergoing surgical tumor resection. Patients with BTC who were admitted to the Department of Visceral and Transplantation Surgery at University Hospital RWTH Aachen for tumor resection were prospectively recruited in 2 cohorts between 2011 and 2017 and enrolled into this study (training cohort: n = 23 patients, validation cohort: n = 95 patients, see Table 1 and Table S1 for detailed patient characteristics). Blood samples were collected prior to surgery and 6–7 days after BTC resection, centrifuged for 10 min at 2,000 g, and serum samples were then stored at −80°C until use. The postoperative timepoint of serum collection was determined for the following reason: Several patients with BTC who were enrolled in this study were referred to our tertiary referral center from peripheral hospitals for surgery only. Because these patients are transferred back to the initial healthcare provider shortly after surgery on a regular basis, we had to collect postoperative serum samples at a rather early postoperative timepoint. Diagnosis of BTC was confirmed histologically in the resected tumor sample. As a control population we analyzed a total of 76 (training cohort: n = 10, validation cohort: n = 66) healthy, cancer-free blood donors with normal values for blood counts, C-reactive protein, kidney and liver function as well as a cohort of 11 patients with primary sclerosing cholangitis (PSC) without evidence of malignancy. Postoperative acute kidney injury (AKI) I was defined according to the KDIGO criteria.19 The study protocol was approved by the ethics committee of the University Hospital RWTH Aachen, Germany (EK 206/09) and conducted in accordance with the ethical standards laid down in the Declaration of Helsinki. Written informed consent was obtained from the patients.

Patient characteristics.

BMI, body mass index; BTC, biliary tract cancer; ECOG PS, Eastern Cooperative Oncology Group performance status.