[Real-world Study of Icotinib in EGFR Mutant Non-small Cell Lung Cancer 
Based on the Therapeutic Drug Monitoring].

BACKGROUND: 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. This study conducted therapeutic drug monitoring (TDM) of Icotinib. The aim of this study was to analyze the drug exposure of Icotinib in targeted therapy for NSCLC, and to investigate the relationship between Icotinib drug concentration and its efficacy and safety. METHODS: Prospective blood samples were collected from NSCLC patients with EGFR-sensitive mutations who received treatment with Icotinib in Peking University Cancer Hospital from April 2022 to July 2024. The drug trough concentration of Icotinib in plasma was detected, and the correlation between drug concentration and efficacy, as well as the toxic side effects, were further analyzed based on the patient's clinical medical records. RESULTS: 22 patients who were treated with Icotinib underwent TDM, but one of them did not acquire the data due to prolonged discontinuation. The remaining 21 patients, each with 1-7 blood draws, obtained a total of 32 plasma drug concentration data. The drug concentration of icotinib is a range of 126.9-2317.1 ng/mL. Among the 21 patients, 18 cases were female (85.7%), and 3 cases were male (14.3%), with an age range of 44-85 years old. The pathological types are all lung adenocarcinoma. Except for 5 patients receiving postoperative adjuvant therapy, 16 patients had assessable tumors. The objective response rate was 43.8% (7/16), and the disease control rate reached 100.0% (16/16). The median value of drug concentration is 805.5 ng/mL among those 21 patients. Compared with the patients who achieved stable disease, the median value of drug concentrations of Icotinib in patients who achieved partial response were 497.2 and 1195.5 ng/mL, respectively (P=0.017). The median value of drug concentrations for patients who did not experience adverse reactions during treatment and those who experienced adverse reactions were 997.0 and 828.6 ng/mL, respectively (P=0.538). CONCLUSIONS: Icotinib demonstrates good therapeutic effect and tolerable toxicity on the EGFR gene mutant NSCLC. There is a certain negative correlation between the plasma drug concentration of Icotinib and its efficacy, while there seems no significant correlation with safety.