Research progress on criteria for discontinuation of EGFR inhibitor therapy

Increase of secondary mutations may be a drug-resistance mechanism for lung adenocarcinoma after radiation therapy combined with tyrosine kinase inhibitor

Objective: To investigate changes in the secondary mutations of tumor in a drug-resistance mechanism for lung adenocarcinoma after radiation therapy combined with tyrosine kinase inhibitor (TKI). Methods: Lung adenocarcinoma cell line PC9 in vitro and xenograft model in nude mice were used to observe tumor inhibitory effects and drug-resistance under the effect of radiation therapy combined with erlotinib through apoptosis detection through in vitro survival curve and in vivo growth curve; changes in gene mutations before and after drug-resistance in nude mice xenografts were observed by the next generation sequencing, and the relationship between cancer drug-resistance and radiation therapy combined with TKI was observed. Results: Radiation therapy combined with erlotinib had a more reliable radio-sensitizing effect in vitro and in vivo, however, there were several drug-resistant tumor cells. Meanwhile, radiation therapy combined with erlotinib could significantly increase the number of mutations in tumor genes. The whole genome sequencing showed that the secondary mutation in the combined treatment group significantly increased in comparison with those of the single treatment group and the blank control group. Conclusion: The increase of secondary mutations may be an important drug-resistance mechanism for lung adenocarcinoma after radiation therapy combined with TKI, which provided further space exploration under the combined action of radiation and TKI.

Research progress on the impact of radiation on TKI resistance mechanisms in NSCLC

Resistance to tyrosine kinase inhibitor (TKI) therapy is often accompanied by various genetic alterations, and radiation is an important weapon for changing the DNA of tumor cells. In radiotherapy combined with TKI therapy for non-small cell lung cancer (NSCLC), the two treatment strategies affect and interact with each other, resulting in complex tumor resistance mechanisms. Accordingly, tumor progression management after radiotherapy combined with TKI therapy should be different from that after TKI therapy alone. However, current clinical practice is entirely based on the resistance mechanisms of simple TKI therapy. Therefore, it is imperative to investigate the impact of radiation on the mechanism of TKI resistance. However, due to the complexity of the resistance mechanisms under the combined effect of both therapies, such studies remain extremely challenging and time-consuming.

MTOR inhibition reversed drug resistance after combination radiation with erlotinib in lung adenocarcinoma

Objective

To investigate the effects of mTOR inhibition on drug resistance in lung adenocarcinoma after combined radiation and erlotinib therapy.

Results

Combined radiation and erlotinib therapy produced clear radiosensitization effects both in vitro and in vivo; however, tumor cells remained drug resistant. Additionally, combined radiation and erlotinib therapy significantly increased p-AKT and p-P70 levels. After mTOR inhibition, the number of surviving cells significantly decreased compared with that before inhibition, and the in vivo growth curve was significantly reduced.

Methods

The effects of combined radiation and erlotinib therapy on tumor inhibition and drug resistance were evaluated by in vitro survival curves in PC9 lung adenocarcinoma cell line and in vivo growth curves in nude mouse xenograft tumor model respectively. The association between tumor drug resistance and the phosphatidylinositol 3-kinase/protein kinase B/mechanistic target of rapamycin (PI3K-AKT-mTOR) pathway was measured by western blot, assessing the changes in protein kinase B (AKT), phosphor-AKT (p-AKT), P70, and p-P70 protein levels. MTOR was inhibited using everolimus, and changes in AKT, p-AKT, P70, and p-P70 levels were observed. Furthermore, changes in in vitro survival curves, and in vivo growth curves before and after mTOR inhibition were evaluated to confirm its effects on drug resistance in lung adenocarcinoma after combined radiation and TKI therapy.

Conclusion

mTOR was associated with drug resistance in lung adenocarcinoma after radiation combined with TKI, and MTOR inhibition reversed drug resistance in lung adenocarcinoma after combined radiation and TKI therapy.

Progress of clinical research on targeted therapy combined with thoracic radiotherapy for non-small-cell lung cancer

The combination of radiotherapy and targeted therapy is an important approach in the application of targeted therapy in clinical practice, and represents an important opportunity for the development of radiotherapy itself. Numerous agents, including epidermal growth factor receptor, monoclonal antibodies, tyrosine kinase inhibitors, and antiangiogenic therapies, have been used for targeted therapy. A number of studies of radiotherapy combined with targeted therapy in non-small-cell lung carcinoma have been completed or are ongoing. This paper briefly summarizes the drugs involved and the important related clinical research, and indicates that considerable progress has been made with the joint efforts of the two disciplines. Many issues, including drug selection, identification of populations most likely to benefit, timing of administration of medication, and side effects of treatment require further investigation. However, further fundamental research and accumulation of clinical data will provide a more comprehensive understanding of these therapies. Targeted therapy in combination with radiotherapy has a bright future.

Role of erlotinib in the targeted treatment of non-small-cell lung cancer in Chinese patients

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) have been demonstrated to improve responses and clinical outcomes significantly in patients with advanced non-small-cell lung cancer (NSCLC). In retrospective subgroup analyses of several studies, patients with Asian ethnicity (including Chinese) are a subpopulation who responds well to EGFR TKI therapy. Since EGFR-mutation status has emerged as an important predictor of a substantially increased benefit, the high mutation rate in the Asian (including Chinese) population could be the explanation for a superior benefit from EGFR TKI therapy. Erlotinib (Tarceva®), one of the EGFR TKIs, has been proved to be effective in second- and third-line therapy, and furthermore in first-line and maintenance settings. In this review, we summarize current data of clinical trials with erlotinib and discuss its role in the targeted treatment of NSCLC in Chinese patients.