Response to pemetrexed rechallenge after acquired resistance of EGFR-TKI in a patient with advanced NSCLC

Acquired resistance of epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) has been developed as an important clinical problem though EGFR-TKI such as gefitinib, erlotinib and afatinib 0005 and 0010 has achieved 8–14 months of progression free survival in advanced non-small cell lung cancer (NSCLC) patient with EGFR mutation. We report a case here that an advanced lung adenocarcinoma with L858R mutation responded well to pemetrexed rechallenge after acquired resistance of erlotinib.     

Anti-tumor activity of a novel EGFR tyrosine kinase inhibitor against human NSCLC in vitro and in vivo

Epidermal growth factor receptor (EGFR) is highly expressed in many human tumors including non-small cell lung cancer (NSCLC). Treatment with epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) has led to dramatic clinical improvement in selected patients with NSCLC. However, intrinsic and acquired resistance to EGFR-TKI remains a common phenomenon. Novel EGFR-TKI, structurally different with erlotinib or gefitinib might be beneficial for patients with NSCLC. In this study, we examined the anti-tumor effect of a newly synthesized novel EGFR tyrosine kinase inhibitor N-(3-chloro-4-fluorophenyl)-N-(7-methoxy-6-(3-morpholinopropoxy) quinazolin-4-yl)-3,3-dimethylbutanamide (F90). In vitro studies in a panel of three different human NSCLC cell lines revealed that F90 inhibited cell proliferation with high potency and induced G0/G1 arrest of cell cycle and apoptosis. F90 markedly reduced phosphorylation of EGFR and inhibited activation of MAPK and Akt. Oral administration of F90 (80 mg/kg/day) to BALB/c nude mice bearing NSCLC cell lines xenografts significantly retarded tumor growth. In conclusion, F90 has potent anti-tumor activity on human lung cancer in vitro and in vivo.     

Overexpression of Cathepsin L is associated with gefitinib resistance in non-small cell lung cancer

Lung cancer, the most common malignancy, is still the leading cause of cancer-related death worldwide. Non-small-cell lung cancer (NSCLC) accounts for 80 % of all lung cancers. Recent studies showed Cathepsin L (CTSL) is overexpressed in various cancerous tissues; however, the association between CTSL expression and EGFR-TKI resistance remains unknown. In this study, we investigated the expression of CTSL in lung cancer specimens and matched normal tissues by quantitative real-time PCR and IHC. The functional role of CTSL in resistant PC-9/GR cell line was investigated by proliferation and apoptosis analysis compared with control PC-9 cells. Our results found that the level of CTSL expression was higher in NSCLC tissues compared with matched normal adjacent tissue samples, and CTSL was more highly expressed in PC-9/GR cells compared to PC-9 cells. Knocking-down of CTSL in PC-9/GR cells could decrease cell proliferation and potentiate apoptosis induced by gefitinib, suggesting CTSL may contribute to gefitinib resistance in NSCLC. CTSL might be explored as a candidate of therapeutic target for modulating EGFR-TKI sensitivity in NSCLC.     

MicroRNA-34a overcomes HGF-mediated gefitinib resistance in EGFR mutant lung cancer cells partly by targeting MET

In non-small-cell lung cancer (NSCLC) that harbours an activating epidermal growth factor receptor (EGFR) mutation, over-expression of hepatocyte growth factor (HGF) is an important mechanism involved in the acquired resistance to EGFR-tyrosine kinase inhibitors (TKIs) by restoring activity of the PI3K/Akt pathway via phosphorylation of MET. In our study, we found that the forced expression of miR-34a inhibited cell growth and induced apoptosis partly by targeting MET in HGF-induced gefitinib-resistant HCC827 and PC-9 cells. Furthermore, dramatic tumour regression was observed in the miR-34a plus gefitinib group in HGF-induced gefitinib resistant mouse xenograft models. This study demonstrates for the first time that miR-34a rescues HGF-induced gefitinib resistance in EGFR mutant NSCLC cells.     

MiR-21 overexpression is associated with acquired resistance of EGFR-TKI in non-small cell lung cancer

Background and purpose

With the increasing use of epidermal growth factor receptor tyrosine kinase inhibitor (EGFR TKI) in patients with advanced non-small cell lung cancer (NSCLC), its acquired resistance has become a major clinical problem. Recent studies revealed that miR-21 was involved into the resistance of cytotoxic agents. The aim of this study was to investigate its role in the acquired resistance of NSCLC to EGFR-TKI.

Methods

EGFR-TKI-sensitive human lung adenocarcinoma cell line PC9 and the acquired resistant cell line, PC9R, were used. Lentiviral vectors were used to infect PC9 or PC9R to regulate the miR-21 expression. The expression of targeted proteins PTEN and PDCD4 was controlled by RNA interference. MicroRNA array, RT-PCR and TaqMan MicroRNA Assays were used to detect miR-21 expression. The MTT and Annexin V assays were used to determine proliferation and apoptosis. Western Blot and immunohistochemistry were used to analyze target protein expression (PTEN, PDCD4, Akt, p-Akt). We also constructed PC9R xenograft tumor model to observe the relationship between miR-21 and EGFR-TKI resistance in vivo and validated it in the clinical serum specimens of NSCLC patients treated with EGFR-TKI.

Result

MiR-21 was overexpressed in the EGFR-TKI resistant cell line PC9R relative to PC9. The level of miR-21 was reversely correlated with the expression of PTEN and PDCD4 and positive correlated with PI3K/Akt pathway. Inhibiting miR-21 with lentivirus vector induces apoptosis in PC9R cell line and inhibiting miR-21with ASO suppressed tumor growth in nude mice treated with EGFR-TKI. Furthermore, serum miR-21 expression in NSCLC patients treated with EGFR-TKI was significantly higher at the time of acquiring resistance than at baseline (p < 0.01).

Conclusion

miR-21 is involved in acquired resistance of EGFR-TKI in NSCLC, which is mediated by down-regulating PTEN and PDCD4 and activating PI3K/Akt pathway.     

VEGF-D基因在肺腺癌、吉非替尼继发耐药肺腺癌及正常肺组织中的表达

背景与目的 表皮生长因子酪氨酸激酶受体抑制剂(epidermal growth factor receptor tyrosine inhibitor,EGFR-TKI)在治疗非小细胞肺癌中逐渐开始发挥重要作用,对EGFR-TKI继发耐药的机制亦日益受到关注.本研究旨在了解血管内皮生长因子D(vascular endothelial growth factor D,VEGF-D)基因在肺腺癌、吉非替尼继发耐药肺腺癌以及正常肺组织中的表达情况,以了解其在吉非替尼继发耐药中的作用.方法 取外科切除的肺腺癌组织及癌旁正常肺组织、吉非替尼继发耐药肺腺癌组织(包括转移的淋巴结).以β-actin为内参照,SYBR Green法实时定量PCR检测VEGF-D基因相对表达水平.确定阳性表达结果后,对表达率和表达水平进行定性和定量分析.结果 对吉非替尼继发耐药肺腺癌(1/6,16.7%)、肺腺癌(7/14,50.0%)和正常肺组织(16/16,100.0%)中VEGF-D基因表达率用计算确切概率值法比较后,三组样本VEGF-D的表达率有显著差别(P=0.000 091 7).7例VEGF-D基因表达阳性的肺癌组织VEGF-D表达水平经非参数检验显著低于对应的正常肺组织(P=0.000).结论 VEGF-D基因在正常肺组织中处于高表达状态,而在肺腺癌组织和吉非替尼继发耐药肺腺癌表达降低,说明其在肺癌及吉非替尼耐药肺癌组织所起的作用不同于正常肺组织.     

Notch pathway regulates osimertinib drug-tolerant persistence in EGFR-mutated non–small-cell lung cancer

Osimertinib is a third-generation epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitor (TKI) that has shown marked antitumor activity in patients with EGFR-mutated non–small-cell lung cancer (NSCLC). However, these effects are transient and most patients develop resistance. Reversible drug-tolerant persister (DTP) cells are defined as a small subpopulation of cells with markedly reduced sensitivity and non-genetic acquired resistance to EGFR-TKIs. Notch is a transmembrane receptor that plays an important role in tumorigenesis. We previously reported that there is significant crosstalk between the Notch and EGFR pathways in NSCLC. Moreover, the Notch pathway is associated with resistance to previous-generation EGFR-TKIs. However, the role of Notch in osimertinib resistance is not fully understood. In this study, we evaluated whether Notch is involved in osimertinib resistance. We show that NOTCH1 and Notch target genes are upregulated in osimertinib DTP cells, and that the addition of a γ-secretase inhibitor (GSI), a Notch inhibitor, impairs drug-tolerant persistence in vitro and in vivo. Compared with osimertinib, combined GSI and osimertinib suppress phospho-ERK partly by enhancing DUSP1 expression. Furthermore, Notch1 and HES1 were upregulated after EGFR-TKI treatment in half of human EGFR-mutated NSCLC tumor tissues. These results suggest that the combination of GSI and osimertinib may be a potential therapy for EGFR-mutated NSCLC.     

Inhibition of mitochondrial glutaminase activity reverses acquired erlotinib resistance in non-small cell lung cancer

The epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) erlotinib has been approved based on the clinical benefit in non-small cell lung cancer (NSCLC) patients over the past decade. Unfortunately, cancer cells become resistant to this agent via various mechanisms, and this limits the improvement in patient outcomes. Thus, it is urgent to develop novel agents to overcome erlotinib resistance. Here, we propose a novel strategy to overcome acquired erlotinib resistance in NSCLC by inhibiting glutaminase activity. Compound 968, an inhibitor of the glutaminase C (GAC), when combined with erlotinib potently inhibited the cell proliferation of erlotinib-resistant NSCLC cells HCC827ER and NCI-H1975. The combination of compound 968 and erlotinib not only decreased GAC and EGFR protein expression but also inhibited GAC activity in HCC827ER cells. The growth of erlotinib-resistant cells was glutamine-dependent as proved by GAC gene knocked down and rescue experiment. More importantly, compound 968 combined with erlotinib down-regulated the glutamine and glycolysis metabolism in erlotinib-resistant cells. Taken together, our study provides a valuable approach to overcome acquired erlotinib resistance by blocking glutamine metabolism and suggests that combination of EGFR-TKI and GAC inhibitor maybe a potential treatment strategy for acquired erlotinib-resistant NSCLC.     

CRKL amplification is rare as a mechanism for acquired resistance to kinase inhibitors in lung cancers with epidermal growth factor receptor mutation

Objectives

Epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors (TKIs) often provide dramatic responses in lung cancer patients with somatic EGFR mutation. However, acquired resistance to the drugs usually emerges within a few years. EGFR T790M secondary mutation, MET gene amplification, and transformation to small cell lung cancer are well-validated mechanisms that underlie acquisition of resistance to EGFR-TKIs. In addition, many molecular aberrations have been reported as candidates for mechanisms of acquired resistance to EGFR-TKIs. Amplification of the CRKL gene was reportedly observed in 1 of 11 lung cancer patients with EGFR mutations who acquired resistance to EGFR-TKI. This study is the first report, to our knowledge, that validated the role of CRKL gene amplification as a mechanism for acquisition of resistance to EGFR-TKIs.

Materials and methods

We analyzed CRKL gene copy numbers, using a quantitative real-time PCR method, in 2 in vitro acquired-resistance cell-line models: 11 clinical samples from patients who developed acquired resistance to EGFR-TKIs, and 39 tumor specimens obtained from 7 autopsy patients whose cancers acquired resistance to EGFR-TKIs. Mutational status of EGFR codon 790 and copy numbers for the MET gene were also determined.

Results and conclusion

In analysis for in vitro models, CRKL gene copy numbers were identical between EGFR-TKI-sensitive parental cells and their acquired resistant descendant cells. In addition, we found no clinical tumor specimens with acquired EGFR-TKI resistance to harbor amplified CRKL genes. These results indicate that CRKL gene amplification is rare in acquisition of resistance to EGFR-TKIs in lung cancer patients with EGFR mutations.     

Reduction of PTEN protein and loss of epidermal growth factor receptor gene mutation in lung cancer with natural resistance to gefitinib (IRESSA)

Gefitinib (IRESSA), an epidermal growth factor receptor (EGFR) tyrosine kinase (TK) inhibitor, has antitumour activity in the advanced non-small-cell lung cancer (NSCLC) setting. However, in chemotherapy-naïve patients with advanced NSCLC, the addition of gefitinib to standard chemotherapy regimens failed to increase survival. These results suggest the need for improved patient selection and combination rationales for targeted therapies. We have identified subpopulations of an adenocarcinoma cell line that are naturally resistant to gefitinib, and have analysed the cDNA expression profiles, genomic status of EGFR gene and the effect of gefitinib on signalling pathways in these cell lines in order to identify key mechanisms for naturally acquired resistance to gefitinib. Gefitinib-resistant subpopulations demonstrated increased Akt phosphorylation (not inhibited by gefitinib), reduced PTEN protein expression and loss of the EGFR gene mutation when compared with parental cell lines. These differences in Akt and PTEN protein expression were not evident from the cDNA array profiles. These data suggests that (1) the EGFR gene mutation may be possibly lost in some cancer cells with other additional mechanisms for activating Akt, (2) reintroduction of PTEN or pharmacological downregulation of the constitutive PI3K–Akt-pathway activity may be an attractive therapeutic strategy in cancers with gefitinib resistance.     

Erlotinib as salvage treatment after failure to first-line gefitinib in non-small cell lung cancer

Purpose

Chemotherapy is the mainstay treatment for advanced non-small cell lung cancer (NSCLC). Gefitinib, an epidermal growth factor receptor—tyrosine kinase inhibitor (EGFR-TKI), has been recently shown to be effective as a first-line treatment in Asian patients with advanced NSCLC, especially for those with favourable clinical features such as female, non-smoker and adenocarcinoma. However, resistance to gefitinib ensues invariably and there is little evidence as for the effectiveness of subsequent salvage treatment. The purpose of this study is to evaluate the efficacy of erlotinib, another EGFR-TKI, after failed first-line use of gefitinib.

Method

Retrospective review of NSCLC patients with favourable clinical features who received gefitinib as first-line treatment and subsequent salvage treatment with erlotinib.

Results

A total of 21 patients with NSCLC were included in the study. Among them, 18 (85.7%) patients had disease control with gefitinib and 12 (57.1%) patients with salvage erlotinib. There was an association between the disease control with gefitinib and erlotinib (p = 0.031). The disease control rate of erlotinib was independent of the chemotherapy use between the two EGFR-TKIs.

Conclusion

For NSCLC patients with favourable clinical features, erlotinib was effective in those who had prior disease control with first-line gefitinib.     

培美曲塞单药或联合吉非替尼治疗EGFR-TKI耐药后晚期非小细胞肺癌临床观察

背景与目的:生长因子受体-酪氨酸激酶抑制剂(epidermal growth factor receptor-tyrosine kinase inhibitor,EGFR-TKI)治疗晚期非小细胞肺癌(non-small cell lung cancer,NSCLC)获得性耐药后尚无标准的治疗方案,亟待探寻有效的后续治疗方法.为临床应用提供指导,该研究旨在比较后续治疗采用培美曲塞单药或联合吉非替尼治疗EGFR-TKI获得性耐药的晚期NSCLC的临床疗效及安全性.方法:入组既往接受过EGFR-TKI治疗后进展的晚期NSCLC患者62例.其中32接受培美曲塞联合吉非替尼治疗,设为联合组;30例单用培美曲塞治疗,设为化疗组.评价临床疗效及不良反应.结果:联合组客观有效率(objective response rate,ORR)为46.9%,高于化疗组的20%,差异有统计学意义(χ2=4.933,P<0.05);两组疾病控制率(disease control rate,DCR)差异无统计学意义(P>0.05);联合组的中位无病生存期(progression-free survival,PFS)为8.0个月,化疗组中位PFS为6.3个月,差异有统计学意义(χ2=8.063,P<0.05),两组总生存期(overall survival,OS)差异无统计学意义(P>0.05).联合组中性粒细胞减少、皮疹的发生率高于化疗组,差异有统计学意义(P<0.05),Ⅲ~Ⅳ不良反应两组差异无统计学意义(P>0.05).结论:晚期NSCLC患者EGFR-TKI获得性耐药后,采用培美曲塞联合吉非替尼较单用培美曲塞显示出更优势临床有效率和中位PFS,不良反应可耐受,值得临床推广运用.     

Phase II Study of the EGFR-TKI Rechallenge With Afatinib in Patients With Advanced NSCLC Harboring Sensitive EGFR Mutation Without T790M: Okayama Lung Cancer Study Group Trial OLCSG 1403

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) as first-line therapy for patients with EGFR-mutated non–small-cell lung cancer (NSCLC) have shown a significantly better objective response rate and progression-free survival than platinum doublet therapy. However, acquired resistance often occurs within 12 months. One of the potential strategies for treating acquired resistance in NSCLC is the readministration of EGFR-TKIs, a strategy that has mainly been evaluated using gefitinib or erlotinib. The aim of the present study is to investigate the efficacy and safety of EGFR-TKI readministration with afatinib in patients with advanced NSCLC harboring activating EGFR mutations without T790M. The primary endpoint is progression-free survival. The secondary endpoints include the objective response rate, disease control rate, overall survival, toxicity, and quality of life. A total of 12 patients will be enrolled in this trial.     

EGFR-TKI治疗非小细胞肺癌研究进展

吉非替尼和厄洛替尼均为小分子量表皮生长因子受体酪氨酸激酶抑制剂(EGFR-TKI),已在化疗失败的晚期非小细胞肺癌(NSCLC)解救治疗中取得疗效,但仅对特定人群发挥作用。EGFR- TKI联合化疗一线治疗NSCLC并未能提高疗效;正在进行的临床研究聚焦于优势人群EGFR-TKI一线治疗或联合化疗的研究。     

大黄素逆转非小细胞肺癌EGFR-TKI耐药的机制研究

目的 探讨大黄素逆转非小细胞肺癌（NSCLC）表皮生长因子受体酪氨酸激酶抑制剂（EGFR TKI）耐药的作用机制。方法 应用持续诱导的方法构建NSCLC EGFR-TKI耐药细胞株HCC827／GR;应用MTS法检测大黄素（30μmol／L）、吉非替尼（1μmol／L）及两药联合处理HCC827和HCC827／GR细胞48h后细胞增殖能力的变化;应用Western blotting法检测HCC827和 HCC827／GR细胞中p EGFR、p-AKT、p-ERK1／2及p-MET蛋白表达水平的变化。结果 MTS法检测结果显示,经单药吉非替尼或大黄素处理后,HCC827／GR细胞增殖能力未减弱,而两药联合处理组的细胞增殖能力明显下降,差异有统计学意义（P＜0.05）。Western blotting检测结果显示,HCC827、HCC827／GR细胞中p-EGFR、p-ERK1/2明显表达,而p-AKT表达微弱;HCC827／GR 中p-MET表达水平较HCC827明显上调。经单药吉非替尼处理后,HCC827细胞株p-EGFR、p-ERK1/2表达水平下调,HCC827／GR细胞株p-EGFR表达明显下调;大黄素可显著下调HCC827／GR细胞株p-MET表达,但对p-EGFR、p-ERK1/2的表达无影响;而大黄素与吉非替尼两药联用可明显抑制HCC827／GR细胞株p-EGFR、p-ERK1/2以及p-MET的表达。结论 大黄素可以逆转NSCLC EGFR-TKI耐药,可能是通过抑制c-Met的活化来实现。     

A Randomized Phase II Study Comparing Nivolumab With Carboplatin-Pemetrexed for Patients With EGFR Mutation–Positive Nonsquamous Non–Small-Cell Lung Cancer Who Acquire Resistance to Tyrosine Kinase Inhibitors Not Due to a Secondary T790M Mutation: Rationale and Protocol Design for the WJOG8515L Study

Antibodies to programmed cell death–1 (PD-1), such as nivolumab, have shown promising clinical activity in patients with advanced non–small-cell lung cancer (NSCLC), but their efficacy appears to be less pronounced in patients with such tumors harboring epidermal growth factor receptor gene (EGFR) mutations. Recent findings suggest that patients with EGFR mutation–positive NSCLC who develop resistance to tyrosine kinase inhibitors (TKIs) due to mechanisms other than acquisition of the secondary T790M mutation of EGFR are more likely to benefit from nivolumab treatment, possibly as a result of a higher level of expression of the PD-1 ligand PD-L1, than are patients who are T790M-positive. The WJOG8515L study (UMIN ID: 000021133) is a randomized phase II trial to compare nivolumab with the combination of carboplatin and pemetrexed in patients with EGFR mutation–positive nonsquamous NSCLC who have developed resistance to EGFR-TKIs due to mechanisms other than T790M. Eligible patients are those with stage IV or recurrent EGFR mutation–positive NSCLC who experience disease progression after therapy with more than 1 EGFR-TKI, including gefitinib, erlotinib, or afatinib; they must show no evidence of the T790M mutation on analysis of a tumor biopsy specimen obtained after progression on such EGFR-TKI therapy, or, if T790M is detected, they must again experience progression on subsequent treatment with a third-generation EGFR-TKI. The primary endpoint is progression-free survival (PFS), and secondary end points include overall survival (OS), objective response rate, duration of response, safety, and OS and PFS according to PD-L1 expression level. Recruitment started in May 2016 and is ongoing.     

非小细胞肺癌中 HGF/c-Met 信号通路与 EGFR-TKI 获得性耐药的关系

表皮生长因子受体酪氨酸激酶抑制剂（EGFR-TKI）为首的靶向药物在晚期非小细胞肺癌患者治疗中取得巨大进展。然而,获得性耐药的出现是其不可避免的结果。肝细胞生长因子（HGF）／c-Met信号通路参与多种肿瘤细胞的形成、迁徙、血管生成等重要细胞进程。该信号通路的异常激活在EGFR-TKI 获得性耐药中发挥了重要作用。实验表明,HGF ／c-Met 信号通路抑制剂可使部分 EGFR-TKI获得性耐药患者临床获益。     

MEK抑制剂在EGFR-TKI靶向治疗非小细胞肺癌中的作用

非小细胞肺癌是最常见的肺癌,最常见的基因突变是EGFR突变,EGFR-TKI已被用于治疗含这类突变的患者。然而,随着治疗进展,患者逐渐出现耐药性导致治疗失败。主要原因是EGFR信号通路下游重新激活,其中RAS/RAF/MEK/ERK和PI3K/AKT/PKC途径最重要。ERK1/2信号再激活可产生对EGFR抑制剂的抗性。目前临床研究已经发现,MEK抑制剂可以抑制ERK磷酸化,从而阻止随后的MAP激酶下游磷酸化,并因此诱导肿瘤活动的退化和停滞。大量试验表明,ERK途径的持续激活有助于获得吉非替尼耐药性。MEK抑制剂还可以诱导细胞周期阻滞和凋亡。本文总结了MEK抑制剂和EGFR-TKI的作用及其在NSCLC治疗中的作用,为肺癌分子靶向治疗提供了新思路。     

Clinical characteristics of non-small cell lung cancer patients who experienced acquired resistance during gefitinib treatment

Background

The NSCLC patients who experienced good clinical responses to an EGFR-TKI will inevitably develop acquired resistance. A great deal of research is being carried out to discover the molecular mechanisms underlying this resistance. In comparison, few studies have been conducted to find out about the clinical characteristics of acquired resistance in the patients who had responded to an EGFR-TKI. Herein we investigated clinical characteristics of NSCLC patients who experienced acquired resistance during gefitinib therapy.

Patients and methods

We reviewed NSCLC patients who showed a clinical benefit from initial gefitinib therapy. All clinical data were obtained from 11 centers of Korean Molecular Lung Cancer Group (KMLCG). The clinical manifestations of acquired resistance, time to progression (TTP), and post-progression survival (PPS) after gefitinib failure were analyzed retrospectively.

Results

A total of 417 patients were recruited. Median TTP was 10.2 months (95% CI, 9.5–10.9). TTP showed a significant longer duration in female, non-smoker, and patients with adenocarcinoma. At the time of acquired resistance, 63.3% of the patients showed symptomatic deterioration. Sites of disease progression were as follows: primary lung lesion in 58.4%, previous metastasis in 38.3%, and new metastasis in 54.2%. Patients with EGFR wild type showed a tendency of higher frequency in symptomatic deterioration and newly development of CNS metastasis compared with patients with EGFR mutation. There was a significant difference in newly development of lung metastasis between patients with exon 19 deletion and those with L858R mutation (41.4% vs. 6.3%, p = 0.02). PPS was 8.9 months (95% CI, 7.4–10.4). Smoking history, PS, new CNS lesion and subsequent chemotherapy were independent factors for PPS.

Conclusion

This study suggests that clinical manifestations of acquired resistance may be different according to EGFR mutation status and EGFR mutation genotype. In addition, subsequent chemotherapy confers clinical benefit in terms of PPS in NSCLC patients who experienced acquired resistance after gefitinib therapy.