Optimal management of patients with non-small cell lung cancer and epidermal growth factor receptor mutations

In recent years, the epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs), gefitinib and erlotinib, which have promising activity and a favourable toxicity profile, have been used in the management of advanced non-small cell lung cancer (NSCLC). The knowledge that EGFR-activating mutations confer sensitivity to EGFR TKIs has led to the design and analysis of phase II and III studies of gefitinib or erlotinib treatment in various clinical scenarios. We review the important NSCLC clinical trials of the efficacy of EGFR TKIs in the context of EGFR-activating mutations. In all phase II single-arm studies or phase III randomized comparative studies, EGFR TKIs as monotherapy were superior to combination chemotherapy in terms of response rate and progression-free survival in patients with activating EGFR mutations. EGFR TKIs have contributed to the superior overall survival time in NSCLC patients with EGFR mutations compared with those patients without EGFR mutations. The results of these studies have led to a paradigm shift in the treatment of patients with advanced NSCLC. NSCLC with EGFR mutations constitutes a new entity requiring different personalized treatment strategies.     

Protein kinase inhibitors to treat non-small-cell lung cancer

Introduction: Activating mutations of the EGFR and rearrangement of anaplastic lymphoma kinase (ALK) best illustrate the therapeutic relevance of molecular characterization in NSCLC patients.

Areas covered: For this review article, all published data on the most relevant Phase III trials with tyrosine kinase inhibitors (TKIs) for the treatment of NSCLC were collected and analyzed.

Expert opinion: Eight Phase III trials clearly established EGFR TKIs as the best therapeutic option for front-line therapy in EGFR-mutated patients. In pretreated NSCLC, EGFR TKIs are considered more effective than standard monotherapy with cytotoxics in presence of classical EGFR mutations, whereas in the EGFR wild-type population, a similar efficacy to docetaxel or pemetrexed in term of survival has been demonstrated. In ALK-translocated NSCLC, a Phase III trial demonstrated the superiority of a multi-target TKI, including ALK, in terms of progression-free survival, response rate and toxicity profile when compared to standard second-line chemotherapy. New agents targeting EGFR or ALK are under evaluation particularly in individuals with acquired resistance to EGFR TKIs or crizotinib.     

The role of EGFR tyrosine kinase inhibitors in the first-line treatment of advanced non small cell lung cancer patients harboring EGFR mutation

Lung cancer continues to be the leading cause of cancer death worldwide. Among lung cancers, 80% are classified as nonsmall- cell lung cancer (NSCLC) and are mostly diagnosed at an advanced stage (either locally advanced or metastatic disease). In the last years, the discovery of the pivotal role in tumorigenesis of the Epidermal Growth Factor Receptor (EGFR) has provided a new class of targeted therapeutic agents: the EGFR tyrosine kinase inhibitors (EGFR-TKIs). Since the first reports of an association between somatic mutations in EGFR exons 19 and 21 and response to EGFR-TKIs, treatment of advanced NSCLC has changed dramatically. Histologic profile, clinical characteristics, and mutational profile of lung carcinoma have all been reported as predictive factors of response to EGFR-TKIs and other targeted therapies. In advanced NSCLC patients harboring EGFR mutations, the use of EGFR TKIs in first-line treatment has provided an unusually large progression-free survival (PFS) benefit with a negligible toxicity when compared with cytotoxic chemotherapy in phase III randomized trials. Considering the findings regarding the excellent benefit and better safety profile of EGFR TKIs in EGFR mutation positive patients, these targeted therapeutic agents can be now considered as first-line treatment in this setting of patients. This review will discuss the new evidences in the role of EGFR-TKIs in the first-line treatment of advanced NSCLC and their implication in the current clinical decision-making.     

Afatinib for the first-line treatment of patients with metastatic EGFR-positive NSCLC: a look at the data

Introduction: Epidermal growth factor receptor (EGFR) mutations are detected in about 10–15% of Caucasian and 30–40% of Asian patients with advanced or metastatic non-small-cell lung cancer (NSCLC). In patients harbouring EGFR mutations, the treatment with different available EGFR tyrosine kinase inhibitors (TKIs) showed to be more effective and safe than platinum-based chemotherapy regimens.

Areas covered: The current evidences about the role of afatinib for patients with EGFR-positive NSCLC are reviewed and discussed. We report a review based on a MEDLINE/PubMed, searched for randomized phase II or III trials evaluating afatinib in EGFR-positive NSCLC.

Expert commentary: Afatinib is the third EGFR TKI approved for the treatment of NSCLC harbouring EGFR mutations, showing high efficacy in this setting of patients.     

Small molecules with EGFR-TK inhibitor activity

Specific and reversible EGFR tyrosine kinase inhibitors (TKI) such as gefitinib and erlotinib are clinically active in advanced or metastatic NSCLC and both are approved in various countries for the treatment of patients that failed prior chemotherapy. Erlotinib has also prolonged survival in pancreatic cancer patients when added to gemcitabine and regulatory approval in this disease is being sought. Additional promising activity has been seen in other tumor types, such as ovarian cancer or head and neck malignancies, and phase III trials in these malignancies are ongoing or planned. Despite these successes, these agents have exhibited anecdotal or modest activity when used as single agents in unselected patients with various other tumor types. We have learned that the clinical development of these agents is far from simple and we need to better understand biological and clinical criteria for patient selection and how to best use the different available agents. The recent discovery of EGFR mutations and the potential identification of other markers that might predict patient response could help to optimize the use of these agents in the future. Irreversible EGFR inhibitors, dual EGF/HER2 and pan-ErbB receptor inhibitors may have greater antitumor activity although the tolerance of these compounds compared to specific EGFR TKIs needs further characterization. HER2 specific TKIs are also in development. Lapatinib, a dual EGFR/HER2 TK inhibitors, is particularly promising in breast cancer. Newer agents, such as BMS-599626, have recently entered into the clinic. In addition to the use of these agents as single agents, many clinical studies are addressing the role of combining them with hormonal agents, biological agents or chemotherapy.     

Epidermal growth factor receptor tyrosine kinase inhibitors in previously treated advanced non-small-cell lung cancer with wild-type EGFR

Introduction: While epidermal growth factor receptor (EGFR) – tyrosine kinase inhibitors (TKIs) lead to longer progression-free survival (PFS) when compared with conventional chemotherapy in non-small-cell lung cancer (NSCLC) harboring activating EGFR mutations, the role of EGFR-TKI remains unclear in EGFR-wild-type (WT) NSCLC.

Areas covered: This article reviews selected data from randomized trials regarding the use of TKIs in EGFR-WT NSCLC. Nine randomized phase III trials have compared EGFR-TKI with chemotherapy in NSCLC patients in a second or later line setting. Two of these trials, TAILOR and DELTA, which were designed to investigate treatment benefits according to EGFR genotype, demonstrated that docetaxel chemotherapy displayed significantly better in progression-free survival (PFS) when compared with the EGFR-TKI erlotinib. Biomarkers to predict clinical benefits of the drug against EGFR WT tumor, and the efficacy of combination regimens using erlotinib or single-use afatinib against tumors are also covered in this article.

Expert opinion: Considering the modest benefits of erlotinib for EGFR-WT tumors, future studies are warranted, including the exploration of useful biomarkers and new treatment strategies for EGFT-TKI use, as well as the development of more sensitive EGFR mutation tests.     

Mechanisms of acquired resistance to epidermal growth factor receptor tyrosine kinase inhibitors and new therapeutic perspectives in non small cell lung cancer

EGFR somatic mutations define a subset of NSCLCs that are most likely to benefit from EGFR tyrosine kinase inhibitors (TKIs). These tumors are dependent on EGFR-signaling for survival. Recently, tyrosine kinase domain somatic mutations have been approved as criterion to decide first-line therapy in this group of advanced NSCLCs. Anyway, all patients ultimately develop resistance to these drugs. Acquired resistance is linked to a secondary EGFR mutation in about a half of patients. Uncontrolled activation of MET, another tyrosine kinase receptor, has been implicated in neoplastic invasive growth. MET is overexpressed, activated and sometimes mutated in NSCLC cell lines and tumor tissues. MET increased gene copy number has also been documented in NSCLC and has been studied as negative prognostic factor. It has also been found in about 20% of patients developing acquired resistance to TKIs inhibitors. In this group, it seems to display a new mechanism, which is able to mark tumor independence from EGFR signaling. The study of delayed resistance mechanisms could lead to the development of new therapeutic strategies. Different molecular alterations could be specifically targeted in order to extend disease control in this group of NSCLCs with distinct clinical and molecular features. EGFR irreversible inhibitors, MET inhibitors and dual EGFR/VEGFR inhibitors represent one of the most challenging issues in current clinical research. Ongoing clinical trials and future perspectives are discussed.     

The fibroblast growth factor receptor signaling pathway as a mediator of intrinsic resistance to EGFR-specific tyrosine kinase inhibitors in non-small cell lung cancer

The EGFR has been targeted through the development of selective tyrosine kinase inhibitors (TKIs) that have proven effective in a subset of non-small cell lung cancer (NSCLC) patients, many bearing gain-of-function EGFR mutations or egfr gene amplification. However, the majority (～80–90%) of NSCLC patients do not respond to EGFR-specific TKIs and a high rate of acquired resistance to these therapeutics is observed in those that do respond. Thus, EGFR-specific TKIs will not, as single agents, make a high impact on overall lung cancer survival. A number of studies support the activities of other receptor tyrosine kinase pathways including cMet, IGF-1R and FGFRs as mechanisms for both intrinsic and acquired resistance to EGFR TKIs. While the role of cMet and IGF-1R signaling systems as mechanisms of resistance to EGFR TKIs has been widely reviewed in recent years, the potential role of FGFR-dependent signaling as a mechanism for EGFR TKI resistance has more recently emerged and will be highlighted herein. Due to the high degree of homology of FGFRs with VEGFRs and PDGFRs, FGFR-active TKIs already exist via development of VEGFR-targeted TKIs as angiogenesis inhibitors. Thus, these agents could be rapidly advanced into clinical investigations as FGFR inhibitors, either alone or in combination with TKIs selective for EGFR, cMet or IGF-1R as a means to expand the spectrum of NSCLC patients that can be effectively targeted with TKI-directed therapies.     

Mechanisms of resistance to epidermal growth factor receptor tyrosine kinase inhibitors in patients with advanced non-small-cell lung cancer: clinical and molecular considerations

Non-Small-Cell Lung Cancer (NSCLC) with somatic mutations of the epidermal growth factor receptor (EGFR) is anticipated to respond to small-molecule tyrosine kinase inhibitors (TKIs) of the EGFR tyrosine kinase. There are, however, patients with EGFR mutated tumors who do not demonstrate tumor response. The most widely accepted mechanism of 'de novo' (inherent) resistance to these TKIs involves mutations of the KRAS gene. KRAS is a downstream mediator of EGFR-induced cell signaling, such mutations appear to be mutually exclusive from EGFR mutations in lung cancer. The first molecular modifier of resistance identified in patients who developed resistance (termed 'acquired resistance') to TK inhibition was a new acquired somatic EGFR mutation (T790M). Today there is an ever-growing series of molecular events that have recently come to the forefront to explain other instances of TKI resistance not attributable to T790M or KRAS. These include a number of molecules that interact with EGFR or form part of its downstream signaling pathway such as HER-2, IGFR-1, MET and B-RAF. Considering that the majority of studies carried out to date with respect to the identification of resistant clones have not used highly sensitive techniques (e.g. allelic discrimination to identify somatic mutations), coupled with the relatively low number of studies examining multiple molecular markers and the accepted molecular heterogeneity of NSCLC raise question as to the existence of 'acquired' versus 'de-novo' resistance. By examining the current knowledge base with respect to mechanisms of resistance to EGFR TKIs in NSCLC, we explore whether 'acquired' resistance is 'de-novo' resistance in disguise, and discuss the promises and limitations of molecular stratification with respect to strategies incorporating TKIs in the treatment of NSCLC.     

Chronicles of EGFR Tyrosine Kinase Inhibitors: Targeting EGFR C797S Containing Triple Mutations

Epidermal growth factor receptor (EGFR) is a receptor tyrosine kinase widely expressed in many cancers such as non-small cell lung cancer (NSCLC), pancreatic cancer, breast cancer, and head and neck cancer. Mutations such as L858R in exon 21, exon 19 truncation (Del19), exon 20 insertions, and others are responsible for aberrant activation of EGFR in NSCLC. First-generation EGFR tyrosine kinase inhibitors (TKIs) such as gefitinib and erlotinib have clinical benefits for EGFR-sensitive (L858R and Del19) NSCLC patients. However, after 10-12 months of treatment with these inhibitors, a secondary T790M mutation at the gatekeeper position in the kinase domain of EGFR was identified, which limited the clinical benefits. Second-generation EGFR irreversible inhibitors (afatinib and dacomitinib) were developed to overcome this T790M mutation. However, their lack of selectivity toward wild-type EGFR compromised their clinical benefits due to serious adverse events. Recently developed third-generation irreversible EGFR TKIs (osimertinib and lazertinib) are selective toward driving mutations and the T790M mutation, while sparing wild-type EGFR activity. The latest studies have concluded that their efficacy was also compromised by additional acquired mutations, including C797S, the key residue cysteine that forms covalent bonds with irreversible inhibitors. Because second- and third-generation EGFR TKIs are irreversible inhibitors, they are not effective against C797S containing EGFR triple mutations (Del19/T790M/C797S and L858R/T790M/C797S). Therefore, there is an urgent unmet medical need to develop next-generation EGFR TKIs that selectively inhibit EGFR triple mutations via a non-irreversible mechanism.     

Dacomitinib for the first-line treatment of patients with EGFR-mutated metastatic non-small cell lung cancer

ABSTRACT

Introduction: Different EGFR tyrosine kinase inhibitors (TKIs) are currently approved for the first-line treatment of NSCLC patients with EGFR mutations. Dacomitinib is an orally administered, second-generation pan-HER inhibitor that has shown to improve PFS and OS compared to the first-generation TKI gefitinib and is the most recent inhibitor to be approved in this setting.

Areas covered: This article will review relevant literature regarding preclinical findings and clinical data from phase I-III trials of dacomitinib. We particularly discuss the mechanism of action of dacomitinib and its clinical efficacy and toxicity as a novel, first-line therapeutic option for EGFR-mutated NSCLC.

Expert commentary: The therapeutic landscape for EGFR-mutated NSCLC has been greatly expanded. In the first-line setting, we have currently first-, second- and third-generation EGFR TKIs available and some combination strategies, including EGFR TKIs with anti-angiogenic drugs or chemotherapy, have also shown to be effective. However, more data are needed to define the optimal therapeutic sequencing of all these targeted agents and combinations. In this view, molecular profiling of tumor tissues and liquid biopsies may provide novel insights on mechanisms of resistance to different drugs and guide treatment decisions.     

EGFR突变肺腺癌脑转移患者放疗结合TKI的最佳时机

目的 探讨表皮生长因子受体(EGFR)突变阳性,脑转移前未使用过酪氨酸激酶抑制剂(TKI)治疗的肺腺癌脑转移患者脑部放疗(BRT)结合TKI治疗的最佳时机.方法 收集50例EGFR突变阳性,脑转移前未使用TKI治疗的肺腺癌脑转移患者的临床资料,分析其治疗方案、疗效及失败模式.结果 50例患者中位随访时间20.0个月,1年总生存率为82.0％,预期生存时间为23个月.单因素分析显示ECOG评分、颅外转移灶、脑转移灶数目、放疗结合靶向时机与总生存期(OS)显著相关.多因素分析显示脑转移灶数目和放疗结合靶向治疗时机与OS有关,先BRT组(BRT结束2周内行TKI治疗)较先TKI组(TKI治疗颅内进展后行BRT)有明显的生存获益(28 m vs 18 m,P=0.011).所有患者1年颅内无进展生存率为60.2％,预期颅内PFS时间为14个月,多因素分析显示ECOG评分、放疗结合靶向时机与颅内PFS显著相关,先BRT组较先TKI组有较好的颅内PFS(17 m vs 10 m,P=0.019).结论 对于EGFR突变阳性、脑转移前未使用过TKI治疗的肺腺癌脑转移患者,放疗结束后行TKI可能是更好的选择.     

Prognostic and predictive value of K-RAS mutations in non-small cell lung cancer

Non-small cell lung cancer (NSCLC) is a heterogeneous disease, caused by the presence of different clinically relevant molecular subtypes. Genetic mutations are emerging as potential biomarkers of response and treatment selection in patients with NSCLC. Over the past few years, activating mutations of epidermal growth factor receptor (EGFR) have been recognized as the most important predictor of response to EGFR tyrosine kinase inhibitors (TKIs) such as gefitinib and erlotinib and also as a favourable prognostic factor. The RAS genes, including H-RAS, K-RAS and N-RAS, encode a family of proteins regulating cell growth, differentiation and apoptosis. Mutations in the K-RAS gene, mainly in codons 12 and 13, have been found in 20-30% of NSCLC tumor samples and occur most commonly, but not exclusively, in adenocarcinoma histology and in heavy smokers. In NSCLC, the presence of K-RAS mutations has generally been considered to be associated with worse prognosis and resistance to systemic therapy in the adjuvant as well as the metastatic setting. In early stage NSCLC, the prognostic role of K-RAS mutations has been evaluated in several studies without definitive conclusion. On the other hand, in advanced NSCLC, the presence of K-RAS mutations identifies a subgroup of patients who do not respond to EGFR-TKI therapy but, at the same time, a positive survival effect from EGFR-TKIs cannot be excluded in these patients. Similarly, K-RAS mutational status does not predict benefit from the anti-EGFR monoclonal antibody cetuximab, highlighting the biological difference between lung cancer and colorectal cancer. As a result of the lack of conclusive data, K-RAS mutations do not represent a validated biomarker for the negative selection of patients who are candidates for anti-EGFR therapy. The aim of this article is to review and discuss the data on the prognostic and predictive value of K-RAS mutations in NSCLC.     

Pharmacotherapy targeting the EGFR oncogene in NSCLC

Introduction: The EGFR plays a central role in regulating cancer cell growth and survival, representing an attractive therapeutic target in NSCLC.

Areas covered: For the purpose of this review article, data from Phase II and III trials with anti-EGFR agents, including EGFR-tyrosine kinase inhibitors (TKIs) and mAbs, were collected and analysed.

Expert opinion: Eight large Phase III trials demonstrated that EGFR-TKIs are the best option we can offer today as front-line therapy exclusively in EGFR mutant NSCLC. In patients with EGFR wild type or unknown lung cancer, platinum-based chemotherapy remains the standard of care, with no consistent benefit produced by the addition of an anti-EGFR treatment. In pretreated NSCLC, EGFR-TKIs are considered more effective than standard monotherapy with cytotoxics in presence of classical EGFR mutations, whereas in the EGFR wild-type population, a similar efficacy with docetaxel or pemetrexed in terms of survival has been demonstrated. New agents targeting EGFR are under investigation, particularly in individuals with squamous cell histology and those with acquired resistance to EGFR-TKIs.     

Successful treatment with erlotinib after gefitinib-induced interstitial lung disease: a case report and literature review

Gefitinib and erlotinib, epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs), are widely used anticancer drugs for patients with non-small cell lung cancer (NSCLC), especially for those with EGFR-activating mutations. Both agents are considered to be less toxic compared with cytotoxic drugs; however, serious adverse events including interstitial lung disease (ILD) which can be fatal occur rarely. After such an event, physicians avoid to use another TKI. In such cases, patients and physicians are forced to make difficult decisions or reluctantly choose TKI when there is no other option. Here we report a case of a patient with lung adenocarcinoma who showed good recovery from gefitinib-induced ILD by high-dose corticosteroid therapy. The patient was then administrated erlotinib as second-line chemotherapy and showed tumor shrinkage without ILD after 6 months of treatment. We discuss the common features of the cases in the previous documentations and ours which were successfully retreated with erlotinib after gefitinib-induced ILD had previously developed.     

Erlotinib for the treatment of brain metastases in non-small cell lung cancer

Introduction: Brain metastases (BM) are a common and lethal complication of non-small cell lung cancer (NSCLC) with up to 40% experiencing this complication. The use of erlotinib, a small molecule epidermal growth factor receptor (EGFR) inhibitor, holds promise in this somewhat refractory cohort of patients, and has become the subject of active clinical investigation.

Areas covered: This review covers the preclinical and clinical studies of erlotonib as it relates to its use in the treatment of NSCLC patients with BM. A literature search in part utilized the PubMed database up through Dec 2015.

Expert opinion: Preclinical and retrospective data for erlotinib provide evidence of CNS penetration, and objective responses in the setting of BM from EGFR mutated NSCLC. Phase I and II data have demonstrated the feasibility of concomitant delivery of erlotinib and WBRT in the treatment of BM from NSCLC. Phase II/III data however, from non-EGFR mutation enriched populations, have demonstrated no benefit in progression free or overall survival with the addition of erlotinib to metastasis directed radiotherapy. Currently the utilization of erlotinib with WBRT or SRS is therefore investigational and may be a reasonable option in erlotinib naïve, EGFR mutated patients with refractory BM.     

Personalized treatment of EGFR mutant and ALK-positive patients in NSCLC

Introduction: The epidermal growth factor receptor (EGFR) is mutated in 15% of adenocarcinomas of the lung. In addition, the anaplastic lymphoma kinase (ALK) is altered in 8% of adenocarcinomas of the lung. Treatment of EGFR mutant and ALK translocation-positive tumors in NSCLC with tyrosine kinase inhibitors (TKI) results in a dramatic therapeutic response and has revolutionized therapy. Unfortunately, resistance to TKIs invariably develops. Many promising new therapies are under investigation to overcome the resistance.

Areas covered: We analyzed the current primary literature and recent national meetings to evaluate the clinical characteristics and therapeutic implications of relevant treatments for EGFR mutant and ALK-positive NSCLC in the first-line, acquired resistance, and adjuvant settings.

Expert opinion: Treatment with EGFR TKIs in the first-line setting of EGFR mutant NSCLC results in a significant clinical benefit. Several promising third generation EGFR TKIs are being evaluated in Phase II and III trials in the acquired resistance setting. Crizotinib is superior to chemotherapy in the first-line setting for ALK-positive NSCLC. Ceritinib is effective and approved for ALK-positive NSCLC in the acquired resistance setting. Continued investigation is needed to develop novel therapies to overcome acquired resistance to TKIs.     

Class act: safety comparison of approved tyrosine kinase inhibitors for non-small-cell lung carcinoma

Introduction: The past decade has seen the development and widespread use of tyrosine kinase inhibitors (TKIs) targeting a mutated EGFR (mEGFR) for the treatment of metastatic NSCLC. We discuss the main properties of the TKIs currently recommended for the treatment of mEGFR NSCLC: gefitinib, erlotinib and afatinib.

Areas covered: The mechanism of action, pharmacodynamics and pharmacokinetics of these drugs, with emphasis on the historical context of their preclinical and clinical development, will be covered, including potential resistance mechanisms to these first-generation TKIs that has driven the trial design for second and third generations of EGFR inhibitors. Six Phase III clinical trials comparing these three TKIs with cisplatin-based chemotherapy upfront for mEGFR NSCLC provide the basis for the comparative safety and toxicity analysis between these agents. Class-related toxicity of these EGFR inhibitors, including life-threatening effects, will be discussed.

Expert opinion: Toxicity and safety analysis from the Phase III trials of these agents in mEGFR populations suggests that afatinib has more frequent and severe side effects. Given that an efficacy advantage has not yet been demonstrated for afatinib over erlotinib and gefitinib, the consistent class toxicity profile of these agents means that gefitinib and erlotinib are a safer first-line treatment recommendation.     

Epidermal growth factor receptor inhibitors in non-small-cell lung cancer

The epidermal growth factor receptor (EGFR) is a cell membrane receptor that plays a key role in cancer development and in the progression of many human malignancies, including non-small-cell lung cancer (NSCLC). EGFR-dependent signaling is involved in cancer cell proliferation, apoptosis, angiogenesis, invasion and metastasis. Targeting the EGFR is a valuable molecular approach in cancer therapy. This receptor is overexpressed in up to 80% of NSCLC cases. Thus, several molecules inhibiting this critical biologic pathway have been synthesized and tested as a single agent or in combination with other anticancer modalities in a wide of clinical trials, including reversible and irreversible small tyrosine kinase inhibitors, such as gefitinib and erlotinib, dual vascular endothelial growth factor receptor EGFR tyrosine kinase inhibitors, such as vandetanib (ZD-6474), and monoclonal antibodies, such as cetuximab, which have shown promising activity in patients with NSCLC. This review focuses on the preclinical and clinical results available with EGFR inhibitors in the treatment of NSCLC patients.     

EGFR基因突变与肿瘤靶向治疗

表皮生长因子受体(epidermal growth factor receptor,EGFR)属于受体酪氨酸激酶超家族,在多种恶性肿瘤中表达。配体与EGFR结合诱导形成二聚体和构象变化,活化酪氨酸激酶及信号转导途径,产生细胞增殖、侵润、转移及抗凋亡等效应。EGFR酪氨酸激酶抑制剂(tyrosine kinase inhibitors,TKIs)类靶向药物,如吉非替尼和厄洛替尼等已应用于临床。临床研究显示仅10%~30%患者对TKIs敏感,部分位于EGFR激酶结构域的活化突变与药物敏感性相关。检测EGFR基因突变有助于预测对药物敏感性和提高疗效。随着治疗绝大多数敏感的患者获得继发耐药性,其中约半数有继发突变T790M,降低药物对靶分子的亲和力,其他许多位于EGFR下游信号途径或旁激活途径的分子也参与耐药形成。因此,未来个体化用药和准确预测敏感性,不仅仅要分析EGFR基因,而且要综合考虑下游和其他信号途径的基因,如PI3K,K-RAS,BRAF,MET和PTEN等。