In the present study, we prospectively examined whether droplet digital polymerase chain reaction (ddPCR) analysis of cell-free DNA (cfDNA) might allow highly specific and quantitative assessment of TKI-sensitizing and T790M resistance mutations of EGFR in patients with advanced NSCLC who acquire resistance to EGFR-TKI therapy. Here, EGFR is linked to non-small cell lung carcinoma.