Determination of KRAS mutant allele frequencies (MAFs) on circulating free tumor DNA (ctDNA) of liquid biopsies might overcome the challenges of invasive tumoral sampling; however, a recent direct comparison of KRAS MAFs to standard serum CA19–9 levels in a large pancreas cancer patient cohort has not shown superiority in prognostication of the liquid biopsy technology [24]. The gene discussed is KRAS; the disease is neoplasm.