Taking together with the results of our previous study,11 and with sputum cytology pathological evaluation as a quality control step, the preliminary data showed that the sputum cfDNA from patients with advanced NSCLC, either treatment‐naïve or acquired resistance, and with malignant sputum can be a surrogate sample, replacing tumor tissues, for detecting either EGFR sensitive mutations or p.T790 M mutation. The gene discussed is EGFR; the disease is neoplasm.