It has been reported that activating KRAS mutation are found in more than 90% of cases of pancreatic ductal adenocarcinoma and accumulate at codon 12 and 13, therefore, tumor-derived DNA circulating from primary tumor tissue into the bloodstream are of interest as a surrogate marker (Bailey et al. 2016; Sugimori et al. 2020; Witkiewicz et al. 2015). The gene discussed is KRAS; the disease is pancreatic ductal adenocarcinoma.