Treatment of Non-small Cell Lung Carcinoma after Failure of Epidermal Growth Factor Receptor Tyrosine Kinase Inhibitor

Article information

Cancer Res Treat. 2013;45(2):79-85

Publication date (electronic) : 2013 June 30

doi : https://doi.org/10.4143/crt.2013.45.2.79

Jae Cheol Lee, MD, PhD ¹, Seung Hun Jang, MD, PhD ², Kye Young Lee, MD, PhD ³, Young-Chul Kim, MD, PhD ⁴

¹Department of Oncology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.

²Division of Pulmonary, Allergy and Critical Care Medicine of Hallym University Sacred Heart Hospital, Hallym University College of Medicine, Anyang, Korea.

³Department of Internal Medicine, Konkuk University School of Medicine, Seoul, Korea.

⁴Department of Internal Medicine, Chonnam National University Hwasun Hospital, Chonnam National University Medical School, Hwasun, Korea.

Correspondence: Young-Chul Kim, MD, PhD. Lung Cancer Clinic, Chonnam National University Hwasun Hospital, 322 Seoyang-ro, Hwasun 519-763, Korea. Tel: 82-61-379-7614, Fax: 82-61-379-7619, kyc0923@chonnam.ac.kr

Received 2013 May 02; Accepted 2013 June 19.

Abstract

Since the first description of non-small cell lung cancer (NSCLC) with activating epidermal growth factor receptor (EGFR) mutation as a distinct clinical entity, studies have proved EGFR tyrosine kinase inhibitors (TKIs) as a first choice of treatment. The median response duration of TKIs as a first-line treatment for EGFR mutant tumors ranges from 11 to 14 months. However, acquired resistance to EGFR-TKIs is inevitable due to various mechanisms, such as T790M, c-Met amplification, activation of alternative pathways (IGF-1, HGF, PI3CA, AXL), transformation to mesenchymal cell or small cell features, and tumor heterogeneity. Until development of a successful treatment strategy to overcome such acquired resistance, few options are currently available. Here we provide a summary of the therapeutic options after failure of first line EGFR-TKI treatment for NSCLC.

Keywords: EGFR tyrosine kinase inhibitor; Non-small-cell lung carcinoma; Drug resistance; Neoplasms

Introduction

Since the first description of non-small cell lung cancer (NSCLC) with activating epidermal growth factor receptor (EGFR) mutation as a distinct clinical entity [1], studies have proved EGFR-tyrosine kinase inhibitors (TKIs) as a first choice of treatment. [2-4]. The median response duration of TKIs as first line treatment for EGFR mutant tumors ranges from 11 to 14 months [2-5].

However, acquired resistance to EGFR-TKIs is inevitable due to various mechanisms, such as T790M, c-Met amplification, activation of alternative pathways (IGF-1, HGF, PI3CA, AXL [6]), transformation to mesenchymal cells [7] or small cell features [8], and tumor heterogeneity [9]. A randomized trial comparing the irreversible ErbB-family blocker afatinib versus placebo in patients with NSCLC after prior EGFR-TKI exposure failed to prove a benefit of overall survival [10]. Another trial comparing dacomitinib versus placebo in a similar clinical setting is ongoing (NCT01000025). Until development of a successful treatment to overcome such acquired resistance, few options are currently available.

Here we provide a summary of the therapeutic options after failure of first line EGFR-TKI treatment for NSCLC.

Change to Other Chemotherapeutic Agents

Because the performance status of patients after failure of first line EGFR-TKI tends to be relatively good, most patients are expected to receive second line treatment. After failure of first line EGFR-TKI, docetaxel, pemetrexed, or platinum doublet with or without bevacizumab can be used as a second line treatment [11]. Pemetrexed is favored because of its low toxicity and relatively good efficacy in EGFR mutant tumors [12]. In cases of squamous cell carcinoma harboring EGFR mutation, pemetrexed and bavacizumab are not indicated.

A chemotherapy regimen capable of achieving long-term disease control after failure of EGFR-TKI would be very helpful. However, no prospective trial comparing the efficacy of these regimens in such a clinical setting has been conducted. A retrospective analysis comparing the efficacy of taxane platinum doublet versus gemcitabine platinum doublet as first line treatments for NSCLC with or without EGFR mutation has been reported [13]. In patients with wild type EGFR, no significant difference was observed in response rate and progression free survival. However, in patients with EGFR mutation, progression free survival of taxane doublet was significantly superior to that of gemcitabine doublet. However, to the best of the author's knowledge, no study for prospective comparison of second line cytotoxic chemotherapy regimens after failure of first line EGFR-TKI has been reported.

A prospective phase II study comparing AUY922 (heat shock protein 90 inhibitor, Novartis) versus docetaxel or pemetrexed in patients who had responded to prior EGFR-TKI and harboring the EGFR mutation (ClinicalTrials.gov, no. NCT01646125) is ongoing.

The importance of re-biopsy of relapsed tumor tissue has recently been emphasized [8]. Because development of acquired resistance to EGFR-TKIs can occur through various mechanisms, such as T790M, c-Met amplification, activation of alternative pathways (IGF-1, HGF, PI3CA, AXL [6]), transformation to mesenchymal cell or small cell features [8], and tumor heterogeneity, molecular studies on relapsed tumor tissues is the most important step in combatting resistance.

Continuation of EGFR-TKIs with or without Other Therapy

1. Asymptomatic progressive disease

When the disease shows progressive disease according to response evaluation criteria such as Response Evaluation Criteria In Solid Tumors (RECIST) [14], the common practice is to switch to a different treatment regimen. However, the National Comprehensive Cancer Network (NCCN) treatment guideline for NSCLC [11] amended the recommendations for continuous use of EGFR-TKI even after development of acquired resistance.

This strategy is supported by the following lines of evidence. When MET amplification is the cause of progression, a MET inhibitor is added to the EGFR inhibitor (MetLung trial, no. NCT01456325). Thus, in order to overcome resistance, EGFR must still be inhibited. In addition, discontinuation of EGFR-TKI can lead to development of "disease flare," a much more accelerated progression of the tumor [15, 16].

Yang et al. [17] recently grouped the pattern of progression after EGFR-TKI as a dramatic, gradual, and local progression. Continuation of EGFR-TKI provided better results than switching to cytotoxic chemotherapy for the gradual progression group. However, they also suggested chemotherapy for the dramatic group with rapid tumor increment, and continuation of EGFR-TKI and local treatment for the local progression group.

2. Progression of brain metastasis

Sometimes, despite adequate control of extracranial tumors, lung cancer shows progression from the brain or leptomeningeal lesions. Jackman et al. [18] reported on a patient who showed isolated progression of leptomengeal metastasis while taking gefitinib 250 mg/day and showed subsequent regression with a higher dose of gefitinib 1,000 mg/day. The cerebrospinal fluid (CSF) concentration of gefitinib 250 mg/day was less than the level required for inhibition of growth of a lung cancer cell line in vitro. When the gefitinib dose was increased to 1,000 mg/day, the resulting CSF concentrations of gefitinib increased above the inhibitory concentration and eventually showed correlation with clinical response.

In the case of crizotinib, which is being used for lung cancer harboring EML4-ALK gene rearrangement, the CSF concentration of crizotinib was very low compared to its plasma concentration [19]. The low drug level in the CSF implies poor blood-brain barrier penetration of TKIs. Thus, the NCCN guideline also recommends continuing EGFR-TKI and addition of local therapy or whole brain radiation treatment [11].

3. Symptomatic relapse of an isolated extra-cranial lesion

Localized relapse such as single supraclavicular lymph node or isolated bony metastasis may be controlled with radiation treatment. In such cases, local treatment with continuing EGFR-TKI can be considered [11]. In a recent report [20] on 18 patients with extracranial local progression, local therapy with continued treatment with an EGFR-TKI was shown to be well tolerated and showed an association with long progression free survival (PFS) and overall survival.

4. Symptomatic relapse with multiple extra-cranial lesions

Changing to another line of systemic anti-cancer treatment should be considered. However, even in such circumstances, EGFR-TKI can also be continued for prevention of disease flare [15, 16].

Switch or Retreatment of EGFR-TKIs Following a Drug Holiday

Most patients who show response to EGFR-TKIs eventually experience disease progression after a median of 12 months. Instead of changing to another chemotherapeutic regimen, the same or a different EGFR-TKI can be re-introduced. In a prospective trial of 10 patients who had previously responded to erlotinib or gefitinib, Riely et al. [16] reported that these patients continued to benefit from retreatment with EGFR-TKI despite documented progression of the disease by RECIST. When patients with acquired resistance to EGFR-TKI discontinued EGFR-TKI treatment, the majority of patients experienced worsening lung cancer symptoms, increased tumor size, and increased fludeoxyglucose (FDG) uptake. Just three weeks after resumption of EGFR-TKI, the majority of patients showed stabilization or improvement of symptoms, decreased tumor size, and reduced tumor FDG uptake.

In several retreatment trials, a switch was made from gefitinib to erlotinib, and in some trials, the same EGFR-TKI was used after a drug holiday or treatment with another line of cytotoxic chemotherapy.

1. Switching from gefitinib to erlotinib

The recommended daily dose of elotinib is near its maximum tolerated dose (MTD) [21]; however, that of gefitinib is only one third of its MTD [22]. Thus, toxicities are more frequent and higher with erlotinib compared with gefitinib. In addition, erlotinib showed survival benefits in squamous cell carcinoma or smokers [23], while gefitinib failed to do so [24]. Thus, in several studies, erlotinib was tried after disease progression due to acquired resistance to gefitinib. Cho et al. [25] reported a response rate of 9.5% and a disease control rate (DCR) of 28.6% among 17 patients who had been previously treated with gefitinib and showed subsequent progression. Other trials have reported a DCR of up to 63% and a median progression free survival of 1.7-6.2 months (Table 1) [25-32].

Table 1

Studies of erlotinib retreatment after gefitinib failure

2. Retrial of the same EGFR-TKI after a drug holiday

Possible differences in the potency of EGFR-TKIs cannot explain every case of second response after re-administration of EGFR-TKI. Similar responses were observed when the same EGFR-TKI was re-used after a drug holiday or treatment with another line of chemotherapy.

Becker et al. [33] reported a response rate of 36% and a DCR of 86% with a second round of erlotinib after a drug holiday (median, 9.5 months). Several trials have reported results of gefitinib retrial after a drug holiday or treatment with another line of chemotherapy. Yokouchi et al. [34], who conducted a retrospective analysis of nine patients, reported a DCR of 89%. Oh et al. [35] prospectively enrolled 20 patients whose tumor had progressed after failure of gefitinib treatment followed by treatment with another line of chemotherapy. After re-introduction of gefitinib, 25% achieved partial remission and 75% showed DCR. However, Asahina et al. [36] reported a DCR of only 44% and a PFS of 2.5 months (Table 2) [33-36].

Table 2

Response to retreatment with the same drug after EGFR-TKI failure

A different response to the same EGFR-TKI regimen after a drug holiday can be explained with tumor heterogeneity. Repopulation of sensitive clones to EGFR-TKI may show a different response to EGFR-TKI in retrial (Fig. 1). In a retrospective analysis of an erlotinib retrial, Becker et al. [33] reported five cases of the T790M mutation and exon 19 deletions in rebiopsy specimens taken before the retrial of erlotinib. Among the five patients with the T790M mutation, two showed partial remission, and one showed stable disease. A selection process due to chemotherapy or to lack of EGFR-TKI may lead to a reduction in the fraction of tumor cells with additional T790M compared to cells exhibiting the activating mutation.

Fig. 1

Schematic tumor volume-time curve according to on-and-off of epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI). Tumor volume is the sum of EGFR-TKI sensitive clones and resistant clones regardless of their molecular mechanisms. The number of EGFR-TKI sensitive clones shows a rapid decrease after initiation of EGFR-TKI, however, that of EGFR-TKI resistant clones shows a steady increase despite EGFR-TKI treatment. Initially, tumor volume reaches partial response (PR) due to decrease of EGFR-TKI sensitive clones, but eventually shows progressive disease (PD) with the increase of EGFR-TKI resistant clones. If EGFR-TKI is discontinued at disease progression, explosive growth of EGFR-TKI sensitive clones can cause disease flare. If EGFR-TKI is reintroduced, EGFR-TKI sensitive clones show a decrease again, and tumor volume can be stabilized (decreasing stable disease [SD] or PR). However, because of increasing EGFR-TKI resistant clones, the duration of tumor volume stabilization would be shorter than that of initial treatment with EGFR-TKI.

Thus, retreatment with the same EGFR-TKI regimen is an option for patients with NSCLC who initially responded to EGFR-TKI treatment and recurred after a drug holiday or treatment with another line of cytotoxic chemotherapy. In view of tumor heterogeneity, resistance mutations such as T790M do not exclude response to EGFR-TKI retreatment.

Next generation of EGFR-TKIs and Combination Strategies

Several strategies for overcoming resistance have been suggested. The ability of irreversible pan-HER inhibitors such as afatinib and dacomitinib to overcome T790M-mediated resistance to gefitinib has been demonstrated in some preclinical studies; therefore, they are being actively investigated.

Dacomitinib showed a better response rate and prolonged response duration compared to erlotinib in patients without prior EGFR-targeted therapy [37]. Similarly, compared with previous studies with first line gefitinib or erlotinib, numerically longer median PFS was achieved by afatinib in EGFR-TKI-naïve patients [38]. However, these second-generation EGFR-TKIs would have limitations in overcoming resistance because results of clinical trials in patients with acquired resistance to EGFR-TKIs have been disappointing [39].

Novel pyrimidine-based, mutant-selective EGFR inhibitors were recently discovered by pharmacological screening of a library of compounds [40]. These are more potent against mutant EGFR regardless of T790M, and less potent against wild type EGFR compared to quinazoline-based EGFR-TKIs, suggesting that use of these drugs could be a promising strategy for treatment of EGFR-TKI resistance.

Another approach for T790M-mediated resistance is the dual inhibition of EGFR with afatinib and cetuximab, an EGFR blocking antibody resembling the synergistic combination of lapatinib and trastuzumab in ErbB2-positive breast cancer. Due to promising preliminary results of activity and tolerability, final results of this regimen are being eagerly anticipated [41]. In selected patients with acquisition of resistance by activated compensatory pathways such as MET and AXL, addition of a MET [42] or AXL [6] inhibitor to EGFR-TKIs could be beneficial.

Conclusion

Development of disease progression eventually occurs after a median duration of 11-14 months after EGFR-TKI treatment in NSCLC harboring activating EGFR mutations. If the progression is localized, continued use of EGFR-TKI along with local treatment such as radiation is recommended. If the tumor shows systemic progression, switching to cytotoxic chemotherapy with or without EGFR-TKI is an option. After a drug holiday or cytotoxic chemotherapy, a second round of EGFR-TKI treatment may show another response.

Notes

Conflict of interest relevant to this article was not reported.

References

1. Lynch TJ, Bell DW, Sordella R, Gurubhagavatula S, Okimoto RA, Brannigan BW, et al. Activating mutations in the epidermal growth factor receptor underlying responsiveness of non-small-cell lung cancer to gefitinib. N Engl J Med 2004;350:2129–2139. 15118073.

2. Maemondo M, Inoue A, Kobayashi K, Sugawara S, Oizumi S, Isobe H, et al. Gefitinib or chemotherapy for non-small-cell lung cancer with mutated EGFR. N Engl J Med 2010;362:2380–2388. 20573926.

3. Mok TS, Wu YL, Thongprasert S, Yang CH, Chu DT, Saijo N, et al. Gefitinib or carboplatin-paclitaxel in pulmonary adenocarcinoma. N Engl J Med 2009;361:947–957. 19692680.

4. Zhou C, Wu YL, Chen G, Feng J, Liu XQ, Wang C, et al. Erlotinib versus chemotherapy as first-line treatment for patients with advanced EGFR mutation-positive non-small-cell lung cancer (OPTIMAL, CTONG-0802): a multicentre, open-label, randomised, phase 3 study. Lancet Oncol 2011;12:735–742. 21783417.

5. Rosell R, Moran T, Queralt C, Porta R, Cardenal F, Camps C, et al. Screening for epidermal growth factor receptor mutations in lung cancer. N Engl J Med 2009;361:958–967. 19692684.

6. Zhang Z, Lee JC, Lin L, Olivas V, Au V, LaFramboise T, et al. Activation of the AXL kinase causes resistance to EGFR-targeted therapy in lung cancer. Nat Genet 2012;44:852–860. 22751098.

7. Nurwidya F, Takahashi F, Murakami A, Takahashi K. Epithelial mesenchymal transition in drug resistance and metastasis of lung cancer. Cancer Res Treat 2012;44:151–156. 23091440.

8. Sequist LV, Waltman BA, Dias-Santagata D, Digumarthy S, Turke AB, Fidias P, et al. Genotypic and histological evolution of lung cancers acquiring resistance to EGFR inhibitors. Sci Transl Med 2011;3:75ra26.

9. Saijo N. Present status and problems on molecular targeted therapy of cancer. Cancer Res Treat 2012;44:1–10. 22500155.

10. Miller VA, Hirsh V, Cadranel J, Chen YM, Park K, Kim SW, et al. Afatinib versus placebo for patients with advanced, metastatic non-small-cell lung cancer after failure of erlotinib, gefitinib, or both, and one or two lines of chemotherapy (LUX-Lung 1): a phase 2b/3 randomised trial. Lancet Oncol 2012;13:528–538. 22452896.

11. National Comprehensive Cancer Network. NCCN Clinical Practice Guidelines in Oncology, Lung Cancer Screening Fort Washington: National Comprehensive Cancer Network; 2013.

12. Wu SG, Yang CH, Yu CJ, Lee JH, Hsu YC, Chang YL, et al. Good response to pemetrexed in patients of lung adenocarcinoma with epidermal growth factor receptor (EGFR) mutations. Lung Cancer 2011;72:333–339. 21111508.

13. Park JH, Lee SH, Keam B, Kim TM, Kim DW, Yang SC, et al. EGFR mutations as a predictive marker of cytotoxic chemotherapy. Lung Cancer 2012;77:433–437. 22521649.

14. Eisenhauer EA, Therasse P, Bogaerts J, Schwartz LH, Sargent D, Ford R, et al. New response evaluation criteria in solid tumours: revised RECIST guideline (version 1.1). Eur J Cancer 2009;45:228–247. 19097774.

15. Chaft JE, Oxnard GR, Sima CS, Kris MG, Miller VA, Riely GJ. Disease flare after tyrosine kinase inhibitor discontinuation in patients with EGFR-mutant lung cancer and acquired resistance to erlotinib or gefitinib: implications for clinical trial design. Clin Cancer Res 2011;17:6298–6303. 21856766.

16. Riely GJ, Kris MG, Zhao B, Akhurst T, Milton DT, Moore E, et al. Prospective assessment of discontinuation and reinitiation of erlotinib or gefitinib in patients with acquired resistance to erlotinib or gefitinib followed by the addition of everolimus. Clin Cancer Res 2007;13:5150–5155. 17785570.

17. Yang JJ, Chen HJ, Yan HH, Zhang XC, Zhou Q, Su J, et al. Clinical modes of EGFR tyrosine kinase inhibitor failure and subsequent management in advanced non-small cell lung cancer. Lung Cancer 2013;79:33–39. 23079155.

18. Jackman DM, Holmes AJ, Lindeman N, Wen PY, Kesari S, Borras AM, et al. Response and resistance in a non-small-cell lung cancer patient with an epidermal growth factor receptor mutation and leptomeningeal metastases treated with high-dose gefitinib. J Clin Oncol 2006;24:4517–4520. 16983123.

19. Costa DB, Kobayashi S, Pandya SS, Yeo WL, Shen Z, Tan W, et al. CSF concentration of the anaplastic lymphoma kinase inhibitor crizotinib. J Clin Oncol 2011;29:e443–e445. 21422405.

20. Yu HA, Sima CS, Huang J, Solomon SB, Rimner A, Paik P, et al. Local therapy with continued EGFR tyrosine kinase inhibitor therapy as a treatment strategy in EGFR-mutant advanced lung cancers that have developed acquired resistance to EGFR tyrosine kinase inhibitors. J Thorac Oncol 2013;8:346–351. 23407558.

21. Hidalgo M, Siu LL, Nemunaitis J, Rizzo J, Hammond LA, Takimoto C, et al. Phase I and pharmacologic study of OSI-774, an epidermal growth factor receptor tyrosine kinase inhibitor, in patients with advanced solid malignancies. J Clin Oncol 2001;19:3267–3279. 11432895.

22. Baselga J, Rischin D, Ranson M, Calvert H, Raymond E, Kieback DG, et al. Phase I safety, pharmacokinetic, and pharmacodynamic trial of ZD1839, a selective oral epidermal growth factor receptor tyrosine kinase inhibitor, in patients with five selected solid tumor types. J Clin Oncol 2002;20:4292–4302. 12409327.

23. Shepherd FA, Rodrigues Pereira J, Ciuleanu T, Tan EH, Hirsh V, Thongprasert S, et al. Erlotinib in previously treated non-small-cell lung cancer. N Engl J Med 2005;353:123–132. 16014882.

24. Thatcher N, Chang A, Parikh P, Rodrigues Pereira J, Ciuleanu T, von Pawel J, et al. Gefitinib plus best supportive care in previously treated patients with refractory advanced non-small-cell lung cancer: results from a randomised, placebo-controlled, multicentre study (Iressa Survival Evaluation in Lung Cancer). Lancet 2005;366:1527–1537. 16257339.

25. Cho BC, Im CK, Park MS, Kim SK, Chang J, Park JP, et al. Phase II study of erlotinib in advanced non-small-cell lung cancer after failure of gefitinib. J Clin Oncol 2007;25:2528–2533. 17577030.

26. Lee DH, Kim SW, Suh C, Yoon DH, Yi EJ, Lee JS. Phase II study of erlotinib as a salvage treatment for non-small-cell lung cancer patients after failure of gefitinib treatment. Ann Oncol 2008;19:2039–2042. 18644828.

27. Viswanathan A, Pillot G, Govindan R. Lack of response to erlotinib after progression on gefitinib in patients with advanced non-small cell lung cancer. Lung Cancer 2005;50:417–418. 16129510.

28. Costa DB, Nguyen KS, Cho BC, Sequist LV, Jackman DM, Riely GJ, et al. Effects of erlotinib in EGFR mutated non-small cell lung cancers with resistance to gefitinib. Clin Cancer Res 2008;14:7060–7067. 18981003.

29. Sim SH, Han SW, Oh DY, Lee SH, Kim DW, Im SA, et al. Erlotinib after Gefitinib failure in female never-smoker Asian patients with pulmonary adenocarcinoma. Lung Cancer 2009;65:204–207. 19110337.

30. Wong AS, Soong R, Seah SB, Lim SW, Chuah KL, Nga ME, et al. Evidence for disease control with erlotinib after gefitinib failure in typical gefitinib-sensitive Asian patients with non-small cell lung cancer. J Thorac Oncol 2008;3:400–404. 18379359.

31. Zhou ZT, Xu XH, Wei Q, Lu MQ, Wang J, Wen CH. Erlotinib in advanced non-small-cell lung cancer after gefitinib failure. Cancer Chemother Pharmacol 2009;64:1123–1127. 19322567.

32. Vasile E, Tibaldi C, Chella A, Falcone A. Erlotinib after failure of gefitinib in patients with advanced non-small cell lung cancer previously responding to gefitinib. J Thorac Oncol 2008;3:912–914. 18670311.

33. Becker A, Crombag L, Heideman DA, Thunnissen FB, van Wijk AW, Postmus PE, et al. Retreatment with erlotinib: Regain of TKI sensitivity following a drug holiday for patients with NSCLC who initially responded to EGFR-TKI treatment. Eur J Cancer 2011;47:2603–2606. 21784628.

34. Yokouchi H, Yamazaki K, Kinoshita I, Konishi J, Asahina H, Sukoh N, et al. Clinical benefit of readministration of gefitinib for initial gefitinib-responders with non-small cell lung cancer. BMC Cancer 2007;7:51. 17374153.

35. Oh IJ, Ban HJ, Kim KS, Kim YC. Retreatment of gefitinib in patients with non-small-cell lung cancer who previously controlled to gefitinib: a single-arm, open-label, phase II study. Lung Cancer 2012;77:121–127. 22333554.

36. Asahina H, Oizumi S, Inoue A, Kinoshita I, Ishida T, Fujita Y, et al. Phase II study of gefitinib readministration in patients with advanced non-small cell lung cancer and previous response to gefitinib. Oncology 2010;79:423–429. 21474967.

37. Ramalingam SS, Blackhall F, Krzakowski M, Barrios CH, Park K, Bover I, et al. Randomized phase II study of dacomitinib (PF-00299804), an irreversible pan-human epidermal growth factor receptor inhibitor, versus erlotinib in patients with advanced non-small-cell lung cancer. J Clin Oncol 2012;30:3337–3344. 22753918.

38. Yang JC, Shih JY, Su WC, Hsia TC, Tsai CM, Ou SH, et al. Afatinib for patients with lung adenocarcinoma and epidermal growth factor receptor mutations (LUX-Lung 2): a phase 2 trial. Lancet Oncol 2012;13:539–548. 22452895.

39. Kwak E. The role of irreversible HER family inhibition in the treatment of patients with non-small cell lung cancer. Oncologist 2011;16:1498–1507. 22016476.

40. Zhou W, Ercan D, Chen L, Yun CH, Li D, Capelletti M, et al. Novel mutant-selective EGFR kinase inhibitors against EGFR T790M. Nature 2009;462:1070–1074. 20033049.

41. Janjigian YY, Groen HJ, Horn L, Smit EF, Fu Y, Wang F, et al. Activity and tolerability of afatinib (BIBW 2992) and cetuximab in NSCLC patients with acquired resistance to erlotinib or gefitinib. J Clin Oncol 2011;29(S):7525.

42. Sadiq AA, Salgia R. MET as a possible target for non-small-cell lung cancer. J Clin Oncol 2013;31:1089–1096. 23401458.

Article information Continued

(open-access, http://creativecommons.org/licenses/by-nc/3.0/) :

This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Reference	No.	CR/PR/SD	PD	PFS (mo)
Lee et al. [26]	23	2	21	6.2
Cho et al. [25]	21	6	15	2
Viswanathan et al. [27]	5	0	5	＜2
Costa et al. [28]	18	4	14	2
Sim et al. [29]	16	4	12	1.7
Wong et al. [30]	21	12	9	3.7
Zhou et al. [31]	21	6	15	1.8
Vasile et al. [32]	8	5	3	5.9

Reference	No.	Drug	CR/PR/SD	PD	PFS (mo)
Asahina et al. [36]	16	Gefitinib	7	9	2.5
Oh et al. [35]	20	Gefitinib	15	5	3.4
Yokouchi et al. [34]	9	Gefitinib	8	1	6.2
Becker et al. [33]	14	Erlotinib	12	2	6.5