A meta‐analysis has shown that p.T790 M mutation emergence during EGFR‐TKI therapy has a negative impact on progression‐free survival (PFS),2 and since tumor tissue biopsy or re‐biopsy is not always viable or effective, analysis of circulating tumor‐derived DNA (ctDNA; also known as liquid biopsy) is a feasible alternative to tissue‐based EGFR mutation testing. The gene discussed is EGFR; the disease is neoplasm.