In patient # 15 who had a KRAS wild type primary tumor, no KRAS mutations could be detected in the CTC-enriched specimen when the patient was in partial response and under treatment with maintenance panitumumab; however, after 4 months of treatment, at the time of disease progression, as documented by the radiological worsening of hepatic lesions and clinical appearance of ascites, the number of CTCs was increased and KRAS mutations could be identified in CTCs-enriched cell fraction. Here, KRAS is linked to neoplasm.