In patients with BTC, significantly higher serum MIC-1 levels were detected in patients with stage IV tumours than in patients with stage I/II/III tumours (526.6 (231.1–788.4) vs. 288.1 (42.7–720.2) × 10–2 ng/ml; p < 0.01) (Fig. 3A), and serum MIC-1 levels showed a significant positive correlation with the UICC stage (r = 0.33; p = 0.01) (Fig. 3B). Here, GDF15 is linked to neoplasm.