In this study, we applied a sensitive multiplex ddPCR-based assay to detect and quantify the seven most common hotspot mutations in codons 12 and 13 (G12A, G12C, G12D, G12V, G12R, G12S, and G13D) of KRAS oncogene in cfDNA isolated from plasma samples obtained from NSCLC patients prior to initiating first-line treatment for recurrent or metastatic disease. This evidence concerns the gene KRAS and non-small cell lung carcinoma.