Double-dose icotinib may induce the emergence of the EGFR exon 20 T790M mutation in non-small cell lung cancer patients harboring EGFR-sensitive mutation

Background

Acquired resistance to epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) inevitably occurs in non-small cell lung cancer (NSCLC) patients harboring EGFR-sensitive mutations. There are approximately half of the patients who developed resistance to EGFR-TKIs treatment, the mechanism of which remains undiscovered. We occasionally found that double-dose icotinib as further-line salvage treatment may induce the emerging mutation of EGFR exon 20 T790M in NSCLC patients. The present study, therefore, was conducted to explore the probability of the emerging T790M mutation after exposure to double-dose icotinib in metastatic NSCLC patients.

Patients and Methods

Metastatic NSCLC patients who received double-dose icotinib as salvage treatment after progression on first-generation TKIs and systematic chemotherapy were screened. Thereafter, patients who received a repeated next-generation sequencing (NGS) test with tumor sample were further enrolled. The procedure of NGS was performed with the standard criteria. Finally, the clinical characteristics, treatment procedures, and outcomes of eligible patients were reviewed and presented.

Results

Three patients have been detected with the emerging T790M mutation after double-dose icotinib exposure, with a mutation frequency of 19.6%, 8.2%, and 87.5%. During the treatment of targetable TKIs including almonertinib or osimertinib, partial response was observed in two patients, and stable disease was observed in the other. The progression-free survival by targetable TKIs for the patients was 3.7+ months (still in extension), 4.9+ months (still in extension), and 6.3 months. Manageable adverse events were observed during the treatment of TKIs.

Conclusion

The results of the present study revealed that the emerging EGFR exon 20 T790M mutation might be induced by double-dose icotinib exposure in further-line treatment. Patients with the emerging T790M mutation responded well to the treatment of targetable TKIs including almonertinib or osimertinib.

[An Overview and Interpretation of Important Clinical Studies on Non-small Cell Lung Cancer in 2021]

Though the coronavirus disease is still raging in 2021, clinical research on non-small cell lung cancer (NSCLC) did not stop. However, benefiting from advances in lung cancer treatment modality, NSCLC patients have experienced significant improvements in overall survival and quality of life. Currently, research advances on targeted therapy and immunotherapy have together transformed the status of postoperative adjuvant therapy and established a new standard treatment modality for resectable NSCLC. There are equally important research advances in locally advanced and advanced NSCLC, including new treatment modalities, new therapeutic agents, etc., all of which bringing more options for clinical treatment. These therapies will bring changes to NSCLC and will gradually lead to the chronicity of lung cancer in the foreseeable future. Therefore, this paper reviews important studies that will change clinical practice in NSCLC treatment and noteworthy research advances in 2021.
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Immunotherapy-based combination strategies for treatment of EGFR-TKI-resistant NSCLC

The rapid development of molecular targeted therapy brings hope to patients with advanced non-small-cell lung cancer (NSCLC). However, drug resistance inevitably occurs during treatment with EGFR-tyrosine kinase inhibitors (TKIs). Osimertinib, a third-generation EGFR-TKI, shows a favorable prognosis in T790M-positive NSCLC. Unfortunately, acquired resistance is still a challenge for both patients and clinicians. There is still no consensus on the optimal treatment. PD-1 and its ligand receptor 1 (PD-L1) inhibitors have yielded great progress, especially in patients with no actionable mutations. In this review, the authors take stock of the relationship between EGFR mutations and PD-L1 expression and summarize the important clinical studies on immunotherapy-inhibitor-based treatment in patients with EGFR-TKI-resistant NSCLC.

Current Therapeutic Strategies and Prospects for EGFR Mutation-Positive Lung Cancer Based on the Mechanisms Underlying Drug Resistance

The discovery of activating mutations in the epidermal growth factor receptor (EGFR) gene and the development of EGFR tyrosine kinase inhibitors (TKIs) have led to a paradigm shift in the treatment of non-small cell lung cancer (NSCLC). EGFR mutation-positive NSCLC is common in East Asia, and approximately 50% of adenocarcinomas harbor EGFR mutations. Undoubtedly, EGFR-TKIs, with their promising efficacy, are the mainstay of primary therapy. However, even if tumor shrinkage is achieved, most patients become resistant to EGFR-TKIs and relapse; hence, EGFR-TKIs do not achieve a radical cure. The problem of the development of resistance to targeted drugs has been a persistent challenge. After the role of EGFR T790M mutation in acquired drug resistance was reported, osimertinib, a third-generation irreversible EGFR-TKI, was designed to overcome the resistance conferred by T790M mutation. In addition, some studies have reported the mechanism of drug resistance caused by mutations other than the T790M mutation and strategies to overcome them. Elucidating the mechanism underlying drug resistance development and combining therapeutic approaches are expected to further improve NSCLC prognosis.