Currently, a ctDNA assay for the detection of EGFR mutations in patients with non-small-cell lung cancer (NSCLC) has been approved by the Food and Drug Administration, and ctDNA assays for EGFR in NSCLC and for KRAS in colorectal cancer are available for commercial use in Europe3,4,45. The gene discussed is EGFR; the disease is non-small cell lung carcinoma.