The concept of monitoring tumour burden and therefore biological effects of treatment by analysing circulating biomarkers has been known for long, but only recently the availability of techniques able to detect circulating tumour DNA has opened new perspectives.5,6 In lung cancer, the first experiences concern EGFR-mutated disease.17,23–27 Recently, Kruger et al.13 explored the role of KRAS mutation in plasma and its changes at different time-points as a marker of early prediction of response to treatment in advanced pancreatic cancer patients treated with first-line chemotherapy. This evidence concerns the gene KRAS and pancreatic neoplasm.