GAST and Zollinger-Ellison syndrome: Gastrin levels at diagnosis did not correlate with OS, although patients who died due to ZES progression had significantly elevated circulating gastrin levels before death (median 16,815 pg/ml, IQR 695.5–59,375) compared to median at diagnosis (1090 pg/ml, IQR 625–1835, p = 0.0098).