Using Real Time PCR, 26/42 (61.9%) cfDNA samples displayed the initial sensitizing EGFR mutation seen at the diagnosis in the primary tumor and 9/42 (21.4%) also showed a concurrent T790M mutation, whereas the remaining cases (16/42, 38.1%) resulted negative for both mutations (Fig. 1a, Additional file 4: Table S4). This evidence concerns the gene EGFR and neoplasm.