Residual ctDNA after treatment predicts early relapse in patients with early-stage non-small cell lung cancer

•Sensitive personalized assays were used to detect ctDNA in 363 plasma samples from 88 patients with early-stage NSCLC.•Exome sequencing of the primary tumour was used to design personalized assays targeting 48 variants unique to each patient.•ctDNA was detected pretreatment in 51% of patients and after treatment in 64.3% who had recurrence of their primary tumour.•Detection at a landmark timepoint after treatment was associated with shorter recurrence-free and overall survival times.•Detection of minimal residual disease after treatment of early-stage NSCLC can identify patients for further intervention. BackgroundIdentification of residual disease in patients with localized non-small cell lung cancer (NSCLC)…