KRAS mutations have been detected in 50% of colorectal cancers and 90% of PDAC [4, 18, 19] and the heterogeneity of KRAS mutations between primary tumor and metastasis in individual patients with PDAC is rare [20, 21], suggesting that, with respect to prognosis, circulating mutant KRAS ctDNA in the blood is a good biomarker for detecting the presence of cancer cells. This evidence concerns the gene KRAS and cancer.