The Association Study Of Non-small Cell Lung Cancer Radiosensitivity Between Epidermal Growth Factor Receptor Gene Status And EGFR-TKI Resistance

ObjectiveNon-small cell lung cancer(NSCLC)is one of the most common malignancies,and approximately 50%-60%of patients have lost the opportunity to be operaed at the time of diagnosis.Radiotherapy plays an important role in the treatment of NSCLC patients.However,there is still lack of predictive factors for the efficancy of radiotherapy in clinic.How to achieve individualized radiotherapy is a huge challenge in clinic.Studies have shown that EGFR mutation status is not only related to the efficacy of EGFR-TKIs,but also may be closely related to radiotherapy sensitivity.The patients with EGFR mutation have better response to radiotherapy.Lee found that patients who with EGFR mutantation and brain metastases had higher local control rate than the patients with EGFR wild-type after radiotherapy(67%vs 50%),and achieved longer intracranial radiation progression-free survival(21m vs 12m).Our previous basic research also found that the EGFR19 exon and 21 exon mutant cell lines were more sensitive to radiation than wild-type cells.However,there are also related studies suggesting that the EGFR gene mutation status is not related to NSCLC radiosensitivity,and most of the existing clinical studies focus on the brain metastasis of lung cancer,while the correlation between extracranial lesions such as the primary site of the lung and EGFR mutation is less,so the exact correlation between EGFR mutation and radiosensitivity is needed to be explored.Targeted therapy is the standard first-line treatment for advanced NSCLC patients with drives gene-positive.However,the resistance of targeted treatment has always been a difficult problem.For patients with locally advanced TKI secondary drug-resistant NSCLC,localized treatments such as targeted radiotherapy are an option to overcome drug resistance clinically.Although basic research has shown that EGFR-TKIs resistance does not affect the radiosensitivity of non-small cell lung cancer,no clinical studies have been reported on whether EGFR-TKIs may affect radiosensitivity after drug resistance.At present,the first-generation and third-generation targeted drugs have been approved for the first-line use of advanced NSCLC.Whether the effects of drug resistance on radiosensitivity are different is still remained unknown.Based on the above research background,The purpose of this study is to explore the association between radiosensitivity and EGFR gene status by using EGFR wild-type and EGFR-sensitive mutants and EGFR-TKI-resistant NSCLC cell lines and to explore the effect of TKI on the sensitivity of radiotherapy after drug resistance.At the same time,we collected 202 patients with advanced NSCLC for retrospective analysis to investigate the efficancy of radiotherapy in both extracranial and intracranial metastases of NSCLC patients with EGFR mutation,and to analysized the effect of TKI on the efficacy of radiotherapy after EGFR-TKI resistance.This study aims to further explore the feasibility of EGFR gene as a predictor of NSCLC radiosensitivity for the individualized radiotherapy in NSCLC patients.Methods1.In vivo study(1)Relationship between EGFR gene status and radiosensitivity of NSCLC cell line:we selected EGFR wild-type adenocarcinoma cell line A549,EGFR mutant cell PC-9,gefitinib-acquired cell line PC-9/ZD,Osimertinib acquired drug-resistant cell line PC-9/ZDOR.The radiosensitivity of each cell line was detected by cloning modeling experiment,and the multi-target model and linear square sum model were clicked to obtain the emission biological parameters of each cell line.(2)Synergistic effect of EGFR-TKI and radiotherapy after drug resistance:We selected two EGFR-TKI resistance cells:PC-9/ZD and PC-9/ZDOR,and added gefitinib and Osimertinib respectively for the same Dose X-ray irradiation.The effect of TKI on the radiosensitivity of each cell line was compared by cloning experiments.2.Clinical study202 NSCLC patients staged III/IV with clear EGFR mutation status were screened from January 2009 to October 2017 in the General Hospital of Southern Command.The patients were divided into the mutation group and the wild group according to the EGFR mutation status.The EGFR mutation status of the patients was retrospectively analyzed.The relationship between the efficiency of radiotherapy,local control time,and the efficacy of TKI combined with radiotherapy was analyzed.3.Statistical methodStatistical analysis was performed using SPSS 23.0 software.Data processing was performed as X±S.T-test was used for comparison between groups.The comparison between radiotherapy efficiency and general clinical features of patients was used X 2 test.The local control time of lesions was used Log-rank test,the difference was statistically significant when P<0.05.Results.1.In vivo study(1)Relationship between EGFR mutation status and radiosensitivity in NSCLC cell line:EGFR mutant cells were significantly more radiosensitive than wild-type cells(P<0.05),There was no difference in radiosensitivity between cell lines carrying T790M secondary mutation and cells not carrying T790M mutationstrains(P>0.05).(2)Synergistic effect of EGFR-TKI and radiotherapy after drug resistance:There was no difference in radiosensitivity after adding gefitinib and Osimertinib in PC-9/ZD and PC-9/ZDOR(P>0.05).2.Clinical study(1)The efficacy of radiotherapy in patients with EGFR mutations was better than wild-type patients:The overall radiotherapy efficiency(ORR)in EGFR mutant patients statistically better than the patients with EGFR wild type(64.8%vs 39%,P<0.05),The overall local control time of EGFR mutant patients was longer than wild-type patients(8.50 vs.4.50 months,P<0.05).(2)Among the EGFR mutation patients,no significant difference was found in radiotherapy efficacy between the 19 exon mutation group and the 21 exon mutation group.(3)There was no significant difference in radiotherapy efficacy between EGFR-TKI sensitive group and EGFR-TKI resistant group.(4)Patients with EGFR-TKI local progression,EGFR-TKI combined with radiotherapy was significantly better than radiotherapy alone:radiotherapy efficiency was 76.9%vs 38.39%(P<0.05),and local control time was 11.50 months vs 8.50 months(P<0.05).Conclusion1.EGFR mutation status may be a molecular predictor of NSCLC radiotherapy sensitivity,The radiosensitivity of cells with EGFR mutation is higer than the cells with EGFR wild type no matter wheather it is EGFR-TKI resistance;2.Clinical studies have shown that for the patients with localized advance of EGFR-TKI,the local control rate of EGFR-TKI combined with radiotherapy is significantly better than that of radiotherapy alone;3.Basic research showed that EGFR-TKI combined with radiotherapy doe s not significantly affect the sensitivity of radiotherapy for EGFR-TKI-resistant cell lines.