As ddPCR is increasingly implemented in clinical practice for detecting somatic mutations that are present at low frequencies in tumors or circulating cell-free DNA, the current study aimed to evaluate the clinical utility of assessing both plasma and tissue EGFR mutations using ultra-sensitive ddPCR assays prior to the treatment and at disease progression in monitoring the efficacies and outcomes of NSCLC patients treated with EGFR-TKIs. Here, EGFR is linked to non-small cell lung carcinoma.