KRAS and neoplasm: Recently, it has been reported that using the Kras mutation of the circulating tumor DNA combined with all other four protein biomarkers, including CA19-9, CEA, hepatocyte growth factor (HGF) and osteopontin (OPN), in the plasma samples of PDAC patients with stage 1 or 2 disease increased the sensitivity of PDAC detection in comparison to circulating tumor DNA alone [44].