Beau-Faller M, Pencreach E, Leduc C, et al. - A total of 366 EGFR-mutated non-small cell lung cancer (NSCLC) persons of the real-life IFCT Biomarkers France study with available pretreatment formalin-fixed paraffin-embedded (FFPE) tumor DNA prior to treatment by first/second-generation EGFR-TKI were investigated in order to evaluate the predominance and clinical importance of quantification of tumor pretreatment T790 M subclones. Droplet digital PCR recognized T790 M in 19/240 specimens. It was detected that ultra-sensitive discovery of tumor T790 M mutation accounted for 8% of EGFR-mutated TKI-naïve NSCLC people and only for T790 M VAF over 1%, it has a negative prognostic value.