Targeting receptor tyrosine kinases in gastric cancer

Molecularly targeted therapeutic agents are constantly being developed and have been shown to be effective in various clinical trials.One group of representative targeted oncogenic kinases,the receptor tyrosine kinases(RTKs),has been associated with gastric cancer development.Trastuzumab,an inhibitor of ERBB2,has been approved for the treatment of gastric cancer,although other receptor tyrosine kinases,such as epidermal growth factor receptor,vascular endothelial growth factor,platelet-derived growth factor receptor,c-Met,IGF-1R and fibroblast growth factor receptor 2,are also activated in gastric cancer.The promising results of the trastuzumab clinical trial for gastric cancer resulted in the approval of trastuzumab-based therapy as a first-line treatment for human epidermal growth factor receptor 2-positive patients.On the other hand,the trial examining bevacizumab in combination with conventional chemotherapy did not meet its primary goal of increasing the overall survival time of gastric cancer patients;however,a significantly higher response rate and a longer progression-free survival were observed in the bevacizumab arm of the trial.Other clinical trials,especially phaseⅢtrials that have tested drugs targeting RTKs,such as cetuximab,panitumumab,gefitinib,erlotinib,figitumumab,sorafenib,sunitinib and lapatinib,have shown that these drugs have modest effects against gastric cancer.This review summarizes the recent results from the clinical trials of molecularly targeted drugs and suggests that further improvements in the treatment of advanced gastric cancer can be achieved through the combination of conventional drugs with the new molecularly targeted therapies.

Epidermal growth factor receptor tyrosine kinase inhibitors for non-small cell lung cancer

First-generation epidermal growth factor receptor tyrosine kinase inhibitors(EGFR-TKIs), including gefitinib and erlotinib, have proven to be highly effective agents for advanced non-small cell lung cancer(NSCLC) in patients harboring an activating EGFR mutation such as the exon 19 deletion mutation and L858 R. Although those reversible small molecular targeted agents provide a significant response and survival benefit, all responders eventually acquire resistance. Secondgeneration EGFR-targeting agents, such as irreversible EGFR/HER2 tyrosine kinase inhibitors and pan-HER TKIs, may improve survival further and be useful for patients who acquired resistance to first-generation EGFR-TKIs. This review discusses novel therapeutic strategies for EGFR-mutated advanced NSCLC using first- and second-generation EGFR-TKIs.

Pathogenesis of RON receptor tyrosine kinase in cancer cells: activation mechanism, functional crosstalk, and signaling addiction

The RON receptor tyrosine kinase, a member of the MET proto-oncogene family, is a pathogenic factor im- plicated in tumor malignancy. Specifically, aberrations in RON signaling result in increased cancer cell growth, survival, invasion, angiogenesis, and drug resistance. Biochemical events such as ligand binding, receptor over- expression, generation of structure-defected variants, and point mutations in the kinase domain contribute to RON signaling activation. Recently, functional crosstalk between RON and signaling proteins such as MET and EFGR has emerged as an additional mechanism for RON activation, which is critical for tumorigenic develop- ment. The RON signaling crosstalk acts either as a regulatory feedback loop that strengthens or enhances tumor- igenic phenotype of cancer cells or serves as a signaling compensatory pathway providing a growth/survival ad- vantage for cancer cells to escape targeted therapy. Moreover, viral oncoproteins derived from Friend leukemia or Epstein-Barr viruses interact with RON to drive viral oncogenesis. In cancer cells, RON signaling is integrated into cellular signaling network essential for cancer cell growth and survival. These activities provide the mo- lecular basis of targeting RON for cancer treatment. In this review, we will discuss recent data that uncover the mechanisms of RON activation in cancer cells, review evidence of RON signaling crosstalk relevant to cancer malignancy, and emphasize the significance of the RON signaling addiction by cancer cells for tumor therapy. Understanding aberrant RON signaling will not only provide insight into the mechanisms of tumor pathogenesis, but also lead to the development of novel strategies for molecularly targeted cancer treatment.

Tyrosine kinase of insulin-like growth factor receptor as target for novel treatment and prevention strategies of colorectal cancer

AIM: To investigate the antineoplastic potency of the novel insulin-like growth factor 1 receptor (IGF-1R) tyro- sine kinase inhibitor (TKI) NVP-AEW541 in cell lines and primary cell cultures of human colorectal cancer (CRC). METHODS: Cells of primary colorectal carcinomas were from 8 patients. Immunostaining and crystal violet stain- ing were used for analysis of growth factor receptor pro- tein expression and detection of cell number changes, respectively. Cytotoxicity was determined by measuring the release of the cytoplasmic enzyme lactate dehydro- genase (LDH). The proportion of apoptotic cells was determined by quantifying the percentage of sub-G1 (hypodiploid) cells. Cell cycle status reflected by the DNA content of the nuclei was detected by flow cytometry. RESULTS: NVP-AEW541 dose-dependently inhibited the proliferation of colorectal carcinoma cell lines and primary cell cultures by inducing apoptosis and cell cycle arrest. Apoptosis was characterized by caspase-3 activa- tion and nuclear degradation. Cell cycle was arrested at the G1/S checkpoint. The NVP-AEW541-mediated cell cycle-related signaling involved the inactivation of Akt and extracellular signal-regulated kinase (ERK) 1/2, the upregulation of the cyclin-dependent kinase inhibitors p21Waf1/CIP1 and p27Kip1, and the downregulation of the cell cycle promoter cyclin D1. Moreover, BAX was upregu- lated during NVP-AEW541-induced apoptosis, whereas Bcl-2 was downregulated. Measurement of LDH release showed that the antineoplastic effect of NVP-AEW541 was not due to general cytotoxicity of the compound. However, augmented antineoplastic effects were ob-served in combination treatments of NVP-AEW541 with either 5-FU, or the EGFR-antibody cetuximab, or the HMG-CoA-reductase inhibitor fluvastatin. CONCLUSION: IGF-1R-TK inhibition is a promising novel approach for either mono- or combination treatment strategies of colorectal carcinoma and even for CRC che- moprevention.

Imipramine protects retinal ganglion cells from oxidative stress through the tyrosine kinase receptor B signaling pathway

Retinal ganglion cell（RGC） degeneration is irreversible in glaucoma and tyrosine kinase receptor B（Trk B）-associated signaling pathways have been implicated in the process.In this study,we attempted to examine whether imipramine,a tricyclic antidepressant,may protect hydrogen peroxide（H_2O_2）-induced RGC degeneration through the activation of the Trk B pathway in RGC-5 cell lines.RGC-5 cell lines were pre-treated with imipramine 30 minutes before exposure to H_2O_2.Western blot assay showed that in H_2O_2-damaged RGC-5 cells,imipramine activated Trk B pathways through extracellular signal-regulated protein kinase/Trk B phosphorylation.TUNEL staining assay also demonstrated that imipramine ameliorated H_2O_2-induced apoptosis in RGC-5 cells.Finally,Trk B-Ig G intervention was able to reverse the protective effect of imipramine on H_2O_2-induced RGC-5 apoptosis.Imipramine therefore protects RGCs from oxidative stress-induced apoptosis through the Trk B signaling pathway.

Therapeutic Effect of First-line Epidermal Growth Factor Receptor Tyrosine Kinase Inhibitor (EGFR-TKI)Combined with Whole Brain Radiotherapy on Patients with EGFR Mutation-positive Lung Adenocarcinoma and Brain Metastases

This study compared the therapeutic effect of first-line epidermal growth factor receptor tyrosine kinase inhibitor(EGFR-TKI)with that of EGFR-TKI plus whole brain radiotherapy(WBRT)on patients with EGFR mutation-positive lung adenocarcinoma and brain metastases.A total of 139 patients with lung adenocarcinoma and brain metastases treated with first-line EGFR-TK1therapy from September 2008 to December 2017 were enrolled in this study.The study endpoints were intracranial time to progression(TTP)and overall survival(OS).The effects of clinical pathological parameters and EGFR gene status on the study endpoints were compared.The results showed that the intracranial TTP was significantly longer in EGFR-TKI plus WBRT group than in EGFR-TKI group (median 30.0 vs.18.2 months,χ2=10.824,P=0.001),but no significant difference in the OS was noted between the two groups (median 48.0 vs.41.1 months,χ2=0.012, P=0.912).Also,there was no statistically significant difference in the OS between patients treated with early and late radiotherapy (P=0.849)and between those with asymptomatic and those with symptomatic intracranial metastases (P=0.189).The OS and intracranial TTP of patients with intracranial oligometastases (≤3metastatic sites)were not significantly different from those of patients with multiple intracranial metastases (P=0.104 and P=0.357,respectively),and exon 19 and exon 21 mutations didn't show significant effects on the OS and intracranial TTP of patients (P=0.418 and P=0.386,respectively).In conclusion,there was no statistically significant difference in the OS between the EGFR-TKI alone group and EGFR-TK1 plus WBRT group.However, simultaneous use of WBRT was found to significantly prolong intracranial TTP and improve cerebral symptoms,and thus EGFR-TKI and WBRT combined may be clinically beneficial for patients with EGFR mutation-positive lung adenocarcinoma and brain metastases.

Plasma Levels of Growth Arrest Specific Protein (Gas6) and the Soluble Form of Its Tyrosine Kinase Receptor Axl (sAxl) in Patients with Hepatocellular Carcinoma

The aim of this study was to determine the plasma levels of vitamin K-dependent protein growth arrest-specific protein 6 (Gas6) and its soluble receptor Axl (sAxl) in patients with hepatocellular carcinoma (HCC), acute hepatitis (AH), fulminant hepatitis(FH), chronic hepatitis (CH), and liver cirrhosis (LC) and to determine whether Gas6 and sAxl can be used as biomarkers. Immunoassys were used to measure levels of plasma Gas6 and sAxl in 40 patients with HCC, 13 patients with AH, 3 patients with FH, 7 patients with LC, and 20 healthy normal adult controls (NC). Furthermore, urinary γ-carboxyglutamic acid (Gla) was measured by high performance liquid chromatography. We have addressed this issue by conducting a cross-sectional study to determine whether plasma Gas6 and sAxl levels are associated with DCP, urinary γ-Gla, and liver functions in humans. Levels of Gas6, sAxl, and γ-Gla were significantly higher in HCC as compared to those in NC, and they were significantly positive correlated. Gas6/sAxl molar ratios in HCC were significantly higher than in NC, but those ratios in AH, FH, and LC were significantly lower in NC. Furthermore, Gas6/sAxl molar ratios in HCC increased significantly in comparison with those AH and LC. The increase of Gas6, sAxl and Gas6/sAxl molar ratio were correlated with the progression and poor prognosis of HCC. Thus, Gas6 and sAxl may be useful biomarkers for HCC.

Levetiracetam induces tyrosine kinase receptor B expression in SH-SY5Y cells

Tyrosine kinase receptor B （TrkB） plays an important role in long-term potentiation and memory formation.The present study used all-trans retinoic acid to induce TrkB expression in SH-SY5Y cells,and observed the effects of levetiracetam （LEV） on TrkB expression.Following exposure to 10,50,and 100 μg/mL LEV,the number of TrkB-positive cells,and average absorbance value were increased.Results demonstrated that LEV can induce TrkB expression in SH-SY5Y cells.

Is there a role for epidermal growth factor receptor tyrosine kinase inhibitors in epidermal growth factor receptor wildtype non-small cell lung cancer?

Non-small cell lung cancer(NSCLC) is the most common type of lung cancer with a world-wide annual incidence of around 1.3 million. The majority of patients arediagnosed with advanced disease and survival remains poor. However, relevant advances have occurred in recent years through the identification of biomarkers that predict for benefit of therapeutic agents. This is exemplified by the efficacy of epidermal growth factor receptor(EGFR) tyrosine kinase inhibitors for the treatment of EGFR mutant patients. These drugs have also shown efficacy in unselected populations but this point remains controversial. Here we have reviewed the clinical data that demonstrate a small but consistent subgroup of EGFR wild-type patients with NSCLC that obtain a clinical benefit from these drugs. Moreover, we review the biological rationale that may explain this benefit observed in the clinical setting.

Effects of insulin receptor tyrosine protein kinase on insulin resistance after scalding in rats

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Role of Tyrosine Kinase Receptors in Growth Factor Mediated Signal Transduction, with Specific Reference to MAPK/Rasand p13k-Akt Containing Pathways in Oncogenesis: A Qualitative Database Review

Receptor Tyrosine kinases (RTKs) play a crucial role in the signal transduction pathways at cellular levels. RTK plays a vital role in cellular communication and transmission of signals to the adjacent cells and regulates different functions of the cell, such as cellular growth, differentiation, metabolism and motility. RTK s triggers growth factor receptors such as epidermal growth factor, insulin growth factor-1 receptor, platelet derived growth factor receptor, and fibro blast growth factor receptor and vascular endothelial growth factor receptor, thereby initiating and regulating cell growth and proliferation. MAPK/RAS and PI3/AKT pathways are the major pathways of RTK’s function. Dysregulation of these RTK’s and pathways often leads to many diseases such as Noonan Syndrome, Logius Syndrome, CFC syndrome and different types of cancer. Point mutation and over expression of receptors and mutations in Ras leads to 30% of human cancers. Also over expression of different growth factor receptors by RTK too lead to several types of cancers as Glioblastoma, Thyroid cancer, Colon cancer and Non-small cell lung cancer. PTEN mutation in PI3/AKT pathway often leads to carcinoma relative to Thyroid, Skin, Large intestine, eye and Bone. Therefore, these RTK’s often used as targets for cancer therapies. The medical sector uses various types of small molecule tyrosine kinase inhibitors such as ATP competitive inhibitors, Allosteric inhibitors and covalent inhibitors which are known as Afatinib, Crizotinib, Eroltinib, Icotinib, Lepatinib and Lenvatinib in treatment and management of differential carcinomas.

Neurotrophic receptor tyrosine kinase family members in secretory and non-secretory breast carcinomas

BACKGROUND Breast cancer is the most common female cancer and a major cause of morbidity and mortality.Progress in breast cancer therapeutics has been attained with the introduction of targeted therapies for specific sub-sets.However,other subsets lack targeted interventions and thus there is persisting need for identification and characterization of molecular targets in order to advance breast cancer therapeutics.AIM To analyze the role of lesions in neurotrophic receptor tyrosine kinase(NTRK)genes in breast cancers.METHODS Analysis of publicly available genomic breast cancer datasets was performed for identification and characterization of cases with fusions and other molecular abnormalities involving NTRK1,NTRK2 and NTRK3 genes.RESULTS NTRK fusions are present in a small number of breast cancers at the extensive GENIE project data set which contains more than 10000 breast cancers.These cases are not identified as secretory in the database,suggesting that the histologic characterization is not always evident.In the breast cancer The Cancer Genome Atlas(TCGA)cohort the more common molecular lesion in NTRK genes is amplification of NTRK1 observed in 7.9% of breast cancers.CONCLUSION Neurotrophin receptors molecular lesions other than fusions are observed more often than fusions.However,currently available NTRK inhibitors are effective mainly for fusion lesions.Amplifications of NTRK1,being more frequent in breast cancers,could be a viable therapeutic target if inhibitors efficacious for them become available.

Role of Nerve Growth Factor (NGF) and Its Receptor Tyrosine Kinase A (TrK A) in Egyptian Cirrhotic Patients with Pruritus

Background: Pruritus is a distressing symptom of cholestatic, inflammatory, and malignant liver diseases. It is a common symptom in many biliary and cholestatic disorders such as primary biliary cirrhosis (PBC). Several mechanisms are generally accepted as possible explanations to the underlying basis of itch. However, the exact pathophysiology of pruritus in liver diseases remains unclear. The cutaneous and central neurobiology of pruritus is complex and underlies a regulation of variable mechanisms. At present, not all mechanisms including neuromediators and receptors are known. Objective: Our objective is to evaluate whether the expression pattern of NGF and its receptor TrK A has a role in pruritus in a group of Egyptian cirrhotic patients. Patients and Methods: Forty Patients with liver cirrhosis were enrolled in the study depending on clinical evidence of stigmata of chronic liver disease (e.g. jaundice, ascites, palmar erythema, spider naevi, etc.) and ultrasonographic features of liver cirrhosis (e.g. coarse echo texture, shrunken liver, etc.). Patients were divided into two groups. Group (1): included 20 patients cirrhotic patients without pruritus. Group (2): included 20 patients cirrhotic patients with pruritus. A group of age and sex matched healthy twenty volunteers as a control. Results: After evaluation of histopathological using hematoxylin and eosin stained sections (H&E) was done. There was positive correlation between NGF protein expression and severity of pruritus in cirrhotic patients with pruritus (r = 0.876, p value ≤ 0.001). Also there was positive correlation between TrK A protein expression and severity of pruritus in cirrhotic patients with pruritus (r = 0.44, p value ≤ 0.05). Conclusions: We report, for the first time, role of these proteins (NGF/TrK A) in the mechanism of pruritus in cirrhotic patients and may provide a potential target for new treatment of pruritus in cirrhotic.

New era of epidermal growth factor receptor-tyrosine kinase inhibitors for lung cancer

Lung cancer is the leading cause of death globally, besides recent advances in its management; it maintains a low 5-year survival rate of 15%. The discovery of epidermal growth factor receptor(EGFR) activating mutations and the introduction of its tyrosine kinase inhibitors(TKIs) have expanded the treatment options for patients with non-small cell lung cancer. Nowadays, EGFR mutation testing is now a common routine for newly diagnosed lung cancer. First generation TKIs developed, erlotinib and gefitinib, were reversible ones. After a median of 14 mo, eventually all EGFR mutated patients develop resistance to reversible TKIs. Afatinib, dacomitinib and neratinib, second generation inhibitors, are selective and irreversible TKIs. Finally, third generation phase Ⅰclinical trials were performed, with lower toxicity profiles, and targeting with more precision the driving clone of this heterogeneous disease.

MicroRNA-760 acts as a tumor suppressor in gastric cancer development via inhibiting G-protein-coupled receptor kinase interacting protein-1 transcription

BACKGROUND Gastric cancer(GC)has become a serious threat to people's health.Accumulative evidence reveals that dysregulation of numerous microRNAs(miRNAs)has been found during malignant formation.So far,the role of microRNA-760(miR-760)in the development of GC is largely unknown.AIM To measure the expression level of miR-760 in GC and investigate its role in gastric tumorigenesis.METHODS Real-time quantitative polymerase chain reaction and Western blot analysis were used to measure the expression of miR-760 and G-protein-coupled receptor kinase interacting protein-1(GIT1).Cell growth was detected by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide(MTT)and cell colony formation assays.Apoptosis was assessed by flow cytometric analysis.The relationship between miR-760 and GIT1 was verified by luciferase reporter assay.RESULTS The results showed that the expression of miR-760 was decreased in GC and associated with poor clinical outcomes in GC patients.Furthermore,miR-760 restrained cell proliferation and cell colony formation and induced apoptosis in GC cells.In addition,miR-760 directly targeted GIT1 and negatively regulated its expression in GC.GIT1 was upregulated in GC and predicted a worse prognosis in GC patients.We also found that upregulation of GIT1 weakened the inhibitory CONCLUSION In conclusion,miR-760 targets GIT1 to inhibit cell growth and promote apoptosis in GC cells.Our data demonstrate that miR-760 may be a potential target for the treatment of GC.

Management of tyrosine kinase inhibitor resistance in lung cancer with EGFR mutation

The identification of driver mutations and drugs that inhibit their activity has been a major therapeutic advance for patients with advanced lung adenocarcinoma. Unfortunately, the success of these drugs is limited by the universal development of resistance. Treatment failure can result from inadequate drug exposure or selection of resistant malignant clones. Clinically distinct mechanisms of disease progression have been identified and can inform treatment decisions. Investigations into the biochemical mechanisms of tyrosine kinase inhibitor resistance may provide additional therapeutic targets by which the efficacy of targeted therapy can be improved.

Efficacy of EGFR Tyrosine Kinase Inhibitors in Non-small Cell Lung Cancer Patients Harboring Different Types of EGFR Mutations:A Retrospective Analysis

With the development of molecular pathology, many types of epidermal growth factor receptor（EGFR） mutations have been identified. The efficacy of EGFR tyrosine kinase inhibitors（EGFR-TKIs） in non-small cell lung cancer（NSCLC） patients with different types of EGFR mutations, especially in patients with single rare mutations or complex mutations（co-occurrence of two or more different mutations）, has not been fully understood. This study aimed to examine the efficacy of EGFR-TKIs in NSCLC patients with different types of EGFR mutations. Clinical data of 809 NSCLC patients who harbored different types of EGFR mutations and treated from January 2012 to October 2016 at Renmin Hospital and Zhongnan Hospital, Wuhan, were retrospectively reviewed. The clinical characteristics of these patients and the efficacy of EGFR-TKIs were analyzed. Among these patients, 377 patients had only the EGFR del-19 mutation, 362 patients the EGFR L858R mutation in exon 21, 33 patients single rare mutations and 37 patients complex mutations. Among these 809 patients, 239 patients were treated with EGFR-TKIs. In all the 239 patients, the disease control rate（DCR） was 93.7% with two patients（0.2%） achieving complete response（CR）, the median progression free survival（PFS） was 13.0 months（95% confidence interval [CI], 11.6–14.4 months）, and the median overall survival（OS） was 55.0 months（95% CI, 26.3–83.7 months）. Subgroup analysis revealed that the DCR in patients harboring single rare or complex mutations of EGFR was significantly lower than in those with del-19 or L858 R mutation（P〈0.001）. Patients with classic mutations（del-19 and/or L858 R mutations） demonstrated longer PFS（P〈0.001） and OS（P=0.017） than those with uncommon mutations（single rare and/or complex mutations）. Furthermore, the patients with single rare mutations had shorter median OS than in those with other mutations. Multivariate Cox regression analysis identified that the type of EGFR mutations was an independent risk factor for PFS（hazard ratio [HR]=0.308, 95% CI, 0.191–0.494, P〈0.001） and OS（HR=0.221, 95% CI, 0.101–0.480, P〈0.001）. The results suggest that the single rare or complex EGFR mutations confer inferior efficacy of EGFR-TKIs treatment to the classic mutations. The prognosis of the single rare EGFR mutations is depressing. EGFR-TKIs may be not a good choice for NSCLC patients with single rare mutations of EGFR. Further studies in these patients with uncommon mutations（especially for the patients with single rare mutations） are needed to determine a better precision treatment.

Tyrosine kinase inhibitors:Multi-targeted or single-targeted?

Since in most tumors multiple signaling pathways are involved,many of the inhibitors in clinical development are designed to affect a wide range of targeted kinases.The most important tyrosine kinase families in the development of tyrosine kinase inhibitors are the ABL,SCR,platelet derived growth factor,vascular endothelial growth factor receptor and epidermal growth factor receptor families.Both multi-kinase inhibitors and singlekinase inhibitors have advantages and disadvantages,which are related to potential resistance mechanisms,pharmacokinetics,selectivity and tumor environment.In different malignancies various tyrosine kinases are mutated or overexpressed and several resistance mechanisms exist.Pharmacokinetics is influenced by interindividual differences and differs for two single targeted inhibitors or between patients treated by the same tyrosine kinase inhibitor.Different tyrosine kinase inhibitors have various mechanisms to achieve selectivity,while differences in gene expression exist between tumor and stromal cells.Considering these aspects,one type of inhibitor can generally not be preferred above the other,but will depend on the specific genetic constitution of the patient and the tumor,allowing personalized therapy.The most effective way of cancer treatment by using tyrosine kinase inhibitors is to consider each patient/tumor individually and to determine the strategy that specifically targets the consequences of altered(epi)genetics of the tumor.This strategy might result in treatment by a single multi kinase inhibitor for one patient,but in treatment by a couple of single kinase inhibitors for other patients.

The relationship between tyrosine kinase inhibitor therapy and overall survival in patients with non-small cell lung cancer carrying EGFR mutations

For patients with epidermal growth factor receptor (EGFR) mutation-positive lung cancer, the relationship between the dose or duration of treatment with tyrosine kinase inhibitor (TKI) and overall survival remains unclear. Here, we analyzed clinical data of 39 patients who were diagnosed with EGFR mutation-positive non-small cell lung cancer and treated with TKI, but subsequently died. Several parameters were measured in this study: overall survival; first, second, and overall TKI therapy durations; first TKI intensity (actual dose/normal dose); and TKI rate (overall TKI therapy duration/overall survival). The response rate to TKI therapy was 50% , and the median survival was 553 days. After TKI therapy failed, 38.5% patients were re-challenged with TKI. We observed a moderate relationship [r = 0.534, 95% confidential interval (CI) = 0.263 to 0.727, P < 0.001] between overall TKI therapy duration and overall survival. However, we found no relationship between overall survival and first TKI intensity (r = 0.073, 95% CI = -0.380 to 0.247, P = 0.657) or TKI rate (r = 0.0345, 95% CI = -0.284 to 0.346, P = 0.835). Nonsmall cell lung cancer patients with mutation-positive tumors remained on TKI therapy for, on average, 33% of the overall survival time. These findings suggest that patients with EGFR mutation-positive tumors should not stick to using TKIs.