<h4>Background</h4>In the real world, the plasma drug concentration range of Icotinib treated with epidermal growth factor receptor (EGFR) gene mutant non-small cell lung cancer (NSCLC) is not yet clear, and there may be a correlation between drug concentration and its efficacy, as well as adverse reactions. The gene discussed is EGFR; the disease is non-small cell lung carcinoma.