When sixteen leftover plasma samples with 20 ng of input cfDNA were used, the EGFR mutations detected in the tumor sample at initial diagnosis were also identified in the cobas® EGFR Mutation Test v2 and the Oncomine Lung cfDNA Assay in nine follow-up plasma samples but not in four out of sixteen patients with lung cancer. The gene discussed is EGFR; the disease is neoplasm.