Originally published as JCO Early Release 10.1200/JCO.2007.14.8494 on May 5 2008

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First-Line Gefitinib in Patients With Advanced Non–Small-Cell Lung Cancer Harboring Somatic EGFR Mutations

Lecia V. Sequist, Renato G. Martins, David Spigel, Steven M. Grunberg, Alexander Spira, Pasi A. Jänne, Victoria A. Joshi, David McCollum, Tracey L. Evans, Alona Muzikansky, Georgiana L. Kuhlmann, Moon Han, Jonathan S. Goldberg, Jeffrey Settleman, A. John Iafrate, Jeffrey A. Engelman, Daniel A. Haber, Bruce E. Johnson, Thomas J. Lynch

From the Massachusetts General Hospital Cancer Center; Dana-Farber Cancer Institute and Department of Medicine, Brigham and Women's Hospital; Department of Pathology, Massachusetts General Hospital; Department of Biostatistics, Massachusetts General Hospital, Boston; Harvard Medical School/Partners Health Care Center for Genetics and Genomics, Cambridge, MA; University of Washington, Seattle, WA; Sarah Cannon Research Institute, Nashville, TN; Fletcher Allen Health Care, Burlington, VT; Fairfax-Northern Virginia Hematology-Oncology PC, Fairfax, VA; Texas Oncology/Sammons Cancer Center, Dallas, TX; University of Pennsylvania, Philadelphia, PA; and the Mt Kisco Medical Group, Mt Kisco, NY

Corresponding author: Lecia V. Sequist, MD, MPH, Massachusetts General Hospital Cancer Center, 32 Fruit St, Yawkey Suite 7B, Boston, MA 02114; e-mail: lvsequist{at}partners.org

	ABSTRACT

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Purpose Somatic mutations in the epidermal growth factor receptor (EGFR) correlate with increased response in patients with non–small-cell lung cancer (NSCLC) treated with EGFR tyrosine kinase inhibitors (TKIs). The multicenter iTARGET trial prospectively examined first-line gefitinib in advanced NSCLC patients harboring EGFR mutations and explored the significance of EGFR mutation subtypes and TKI resistance mechanisms.

Patients and Methods Chemotherapy-naïve patients with advanced NSCLC with 1 clinical characteristic associated with EGFR mutations underwent direct DNA sequencing of tumor tissue EGFR exons 18 to 21. Patients found to harbor any EGFR mutation were treated with gefitinib 250 mg/d until progression or unacceptable toxicity. The primary outcome was response rate.

Results Ninety-eight patients underwent EGFR screening and mutations were detected in 34 (35%). EGFR mutations were primarily exon 19 deletions (53%) and L858R (26%) though 21% of mutation-positive cases had less common subtypes including exon 20 insertions, T790M/L858R, G719A, and L861Q. Thirty-one patients received gefitinib. The response rate was 55% (95% CI, 33 to 70) and median progression-free survival was 9.2 months (95% CI, 6.2 to 11.8). Therapy was well tolerated; 13% of patients had grade 3 toxicities including one grade 3 pneumonitis. Two patients with classic activating mutations exhibited de novo gefitinib resistance and had concurrent genetic anomalies usually associated with acquired TKI resistance, specifically the T790M EGFR mutation and MET amplification.

Conclusion First-line therapy with gefitinib administered in a genotype-directed fashion to patients with advanced NSCLC harboring EGFR mutations results in very favorable clinical outcomes with good tolerance. This strategy should be compared with combination chemotherapy, the current standard of care.

	INTRODUCTION

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Non–small-cell lung cancer (NSCLC) is an aggressive neoplasm, responsible for more cancer deaths each year in the United States than colon, breast, pancreas, and prostate cancers combined.¹ Cytotoxic chemotherapy offers a modest benefit for patients with advanced NSCLC, with response rates of 20% to 35% and median survival of 10 to 12 months.^2-4 The oral small molecule epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) gefitinib and erlotinib are active after chemotherapy in the general, unselected NSCLC population, with responses in 10% to 18%, a 2-month median survival advantage over placebo for erlotinib, and noninferiority compared with docetaxel for gefitinib.^5-8

The discovery of somatic mutations in the TK domain of EGFR in NSCLC represents a dramatic step in elucidating genomic changes in lung cancer and their role in developing treatment strategies.^9-11 These gain-of-function mutations enhance EGFR activation, markedly increase sensitivity to EGFR TKIs, and are transforming.^9,12,13 Retrospective studies suggest particularly promising results with EGFR TKI therapy among patients harboring EGFR mutations, with response rates higher than 65% and median survival of 20 to 30 months.^9-11,14-17 Characteristics associated with EGFR mutations enable clinical profiling of patients to enrich for mutations among patients with NSCLC.^5,6,14,18,19

While most patients with EGFR mutations derive benefit from EGFR TKIs, there is variability in degree and duration of response. Some patients exhibit de novo resistance, and the remainder are highly likely to develop acquired resistance after a period of initial response. De novo resistance mechanisms among patients with EGFR mutations have not been well studied, though two genomic mechanisms of acquired resistance are recognized, including a secondary point mutation in EGFR (T790M) that blocks the capacity for gefitinib or erlotinib to inhibit EGFR, and amplification of MET, which activates similar downstream signaling pathways, obviating the actions of EGFR TKIs.^20-22

We conducted this multicenter clinical trial to prospectively assess the potential benefit and toxicity of first-line gefitinib therapy in patients with advanced NSCLC harboring EGFR mutations. We also aimed to explore the significance of the different EGFR mutations and the role of EGFR TKI resistance mechanisms.

	PATIENTS AND METHODS

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Study Design and Patients
We recruited patients to this phase II, prospective, multicenter trial using a two-step process of clinical eligibility screening followed by EGFR mutation testing. Only patients with an EGFR mutation were eligible for treatment. Clinical eligibility included stage IIIB with pleural effusion or stage IV NSCLC, measurable disease by Response Evaluation Criteria in Solid Tumors (RECIST),²³ performance status 2 by Eastern Cooperative Oncology Group (ECOG) criteria,²⁴ adequate hematologic, renal, and hepatic function, and one characteristic associated with mutations (female sex, adenocarcinoma histology of any subtype, never-smoking history, East Asian ethnicity). Never-smoking was defined as 100 cigarettes.²⁵ Patients with squamous cell tumors, prior systemic therapy for advanced NSCLC, CNS metastases without definitive treatment, clinically active interstitial lung disease, or other clinically significant cancers within 5 years were not eligible.

EGFR Mutation Screening
Patients were required to have available tumor tissue (fresh frozen or paraffin embedded) from the primary tumor or a metastatic site for mutation screening. EGFR mutation testing was performed centrally at the Clinical Laboratory Improvement Amendment–certified Laboratory for Molecular Medicine within Harvard Medical School/Partners HealthCare Center for Genetics and Genomics (performed by V.A.J.). Although it is now recognized that overlapping in-frame deletions in exon 19 and the exon 21 mutation L858R are the EGFR mutations most commonly identified and most clearly associated with TKI responsiveness,^15-17,26,27 our study was designed shortly after EGFR mutations were discovered and allowed any EGFR somatic mutation. The kinase domain exons 18 to 24 and their flanking intronic regions were amplified and sequenced for EGFR mutations using standard procedures previously published.²⁸ After study initiation, the protocol was amended to screen only exons 18 to 21 because both our own experience and the growing body of literature lacked reports of mutations in EGFR exons 22, 23, or 24. Any confirmed somatic mutation was sufficient to allow entry into the study.

Fluorescent In Situ Hybridization Analyses
The tumor samples were tested for EGFR gene copy number via fluorescent in situ hybridization (FISH) using standard procedures and employing fluorescent probes for the EGFR locus on chromosome 7p (bacterial artificial chromosome [BAC] CTD-2113A18) and for chromosome 7q (BAC RP5-1129E22) as a reference (performed by M.H., A.J.I.). Samples were considered to have increased copy number (FISH-positive) if they exhibited EGFR gene amplification and/or chromosome 7 high polysomy using criteria described previously.²⁹ Five patients underwent FISH analysis for MET amplification using standard procedures and employing BAC probe CTB-13N12 and the EGFR probe as a control (performed by G.K., A.J.I.).²²

Treatment and Evaluation
Patients were treated with 250 mg of daily oral gefitinib continuously until progression or intolerable adverse effects. Each cycle was 28 days. A pill diary was kept to monitor compliance and patients were instructed to make up missed doses only if this could be done 12 hours before the subsequent dose. Dose interruptions were recommended for the initial management of treatment-related toxicities; in the case of recurrent toxicity, a dose reduction to 250 mg every other day was allowed.

Safety assessments including history, physical examination, and laboratory evaluations were performed before therapy initiation, on day 8, at the beginning of each cycle for the first six cycles, then bi-monthly. Toxicities were graded per the National Cancer Institute Common Toxicity Criteria (version 3.0).³⁰ Efficacy was assessed in an intent-to-treat manner with computed tomography (CT) scans after cycle 1 and then bi-monthly. All radiographs were centrally reviewed at Massachusetts General Hospital by a team of study radiologists. Responses were categorized per RECIST and are reported as best response achieved per patient.²³ A designation of partial response required confirmation after 4 to 8 weeks and a designation of stable disease required lack of progression for 4 weeks. One patient did not undergo efficacy CT scans due to treatment-related pneumonitis and was assumed a nonresponder in all analyses.

Statistical Considerations
The primary end point of the study was response rate, calculated as the sum of patients with confirmed complete and partial responses divided by the number of patients treated. The goal sample size was 30 EGFR mutation–positive patients. The anticipated response rate based on the prior literature was conservatively estimated to be 30%. With 30 mutation-positive patients we could detect a true response rate of 30% with a 95% CI of 14% to 46%. The association between clinical characteristics and EGFR mutations and the comparison of response rates among patient subgroups were evaluated with Fisher's exact test. Time to progression (TTP) was the interval from enrollment to documented disease progression and survival was the interval from enrollment to death. Progression-free survival (PFS; survival without disease progression or death) and overall survival (OS) were calculated using the Kaplan-Meier method. TTP was compared among patient subgroups using Wilcoxon rank sum tests or Kruskall-Wallis tests.

The clinical trial protocol was approved and monitored by the local institutional review board at all sites and all patients provided written informed consent. Data were compiled and analyzed centrally at Massachusetts General Hospital.

	RESULTS

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Patients
We screened 98 patients from 11 centers for EGFR mutations from November 2004 to October 2006 and confirmed that 34 patients (35%) harbored mutations. Three (4%) of 98 samples were not assessable due to insufficient material or failure to polymerase chain reaction (PCR)–amplify DNA. Characteristics of the 98 screened and 34 mutation-positive patients are summarized in Table 1. Among this clinically prescreened group, never-smoking was the only characteristic that predicted EGFR mutation status (P = .02).

View larger version (12K): [in this window] [in a new window] [PowerPoint Slide for Teaching]   Fig 1. Percent change in measurable tumor at best response, by individual patient. The sum tumor diameter was measured in centimeters using Response Evaluation Criteria in Solid Tumors at baseline and at the time of best response. All but four patients had an overall decrease in their measurable tumor diameter. The dashed line denotes a decrease in tumor size of 30%, which is the definition of a partial response, while an increase of 20% defines progressive disease (PD). Note that both patients with PD as their best response progressed in nonmeasurable anatomic areas. The patients are also displayed by mutation type: del 19 in blue, L858R in yellow, and atypical mutations in grey.

View larger version (10K): [in this window] [in a new window] [PowerPoint Slide for Teaching]   Fig 2. Kaplan-Meier curves for (A) progression-free survival and (B) overall survival among all treated patients.

In addition, a 41-year-old man with a left lung adenocarcinoma and metastatic disease throughout the skeleton was found to harbor del 19. Two weeks after initiating gefitinib, he complained of breathlessness and was found to have pulmonary emboli and a new moderate-sized pericardial effusion that proved malignant on cytologic examination. Repeat CT scan on day 22 confirmed PD. He was removed from study and received cytotoxic chemotherapy, but died after 5.5 months. Genomic studies of his tumor did not identify a T790M EGFR mutation or K-Ras mutation (commonly associated with de novo resistance³¹). We examined the tumor specimen using FISH and found clear evidence of substantial MET amplification (Fig 3). Twelve additional tumor specimens from patients with NSCLC with either del 19 or L858R EGFR mutations that responded to gefitinib did not have any concurrent MET amplification (²² and data not shown).

View larger version (59K): [in this window] [in a new window] [PowerPoint Slide for Teaching]   Fig 3. Concurrent del 19 EGFR mutation and MET amplification in a patient with non–small-cell lung cancer (NSCLC) with de novo resistance to gefitinib. The photograph depicts the fluorescent in situ hybridization analysis for MET (red) and EGFR (green) copy number using gene-specific bacterial artificial chromosome probes. The cancer cells have substantial amplification of the MET locus with an average of 12 MET signals per cell.

	DISCUSSION

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We have demonstrated that genotype-directed EGFR TKI therapy with gefitinib for patients with previously untreated NSCLC is feasible in a US population and well tolerated. Moreover, we found significant clinical benefit with an ORR of 55%, median PFS of 9.2 months, and median OS of 17.5 months, approximately two-fold greater than typical results with cytotoxic regimens in unselected NSCLC populations.^2-4 This supports the emerging paradigm of treating biologically defined populations with targeted agents. Importantly, we found that one third of screened patients had detectable EGFR mutations using simple prescreening criteria. This is in contrast to the approximately 10% incidence of mutations in the general US NSCLC population, implying that clinical characteristics represent an effective strategy to enrich patients for successful molecular screening.

Compared with standard first-line therapy for NSCLC, the toxicity of gefinitib was favorable. Four (13%) of 31 patients experienced grade 3 toxicities, there were no grade 4 events, only one patient (3%) was removed from treatment for toxicity. In contrast, standard combination chemotherapy typically yields hematologic and gastrointestinal grade 3 to 4 toxicities in 25% to 75% of patients, with 9% to 27% discontinuing for intolerance.^2-4

Our results are consistent with three other phase II studies of first-line EGFR TKIs in mutation-positive NSCLC. Two studies have been completed in Japanese populations. Inoue et al³² screened 75 tumors available in their pathology department from patients with treatment-naïve advanced NSCLC and identified 25 (33%) with del 19 or L858R EGFR mutations, obtained consent for 16 patients (64%) for treatment with first-line gefitinib, and observed an ORR of 75% and median PFS of 9.7 months. These authors did not specify how tumors were identified for mutation screening. In a prospective clinical trial, Asahina et al³³ screened 82 patients with advanced NSCLC, identified 20 (24%) with del 19 or L858R mutations, treated 16 (80%) with first-line gefitinib, and observed a response in 12 (75%) and a median PFS of 8.9 months. Finally, Paz-Ares et al³⁴ performed a prospective study nested within a larger trial using the EGFR TKI erlotinib in Spanish patients. Preliminary report indicates that tumors from 1,047 patients were analyzed in the parent study, 428 of which had treatment-naïve advanced disease and thus were screened for del 19 and L858R EGFR mutations. Sixty-seven (19%) were mutation positive and 43 (64%) were enrolled in first-line erlotinib, achieving an ORR of 82% and a PFS of 13.3 months.

Our study expands on these studies in several ways. We treated patients with any type of EGFR mutation, enabling analysis of clinical benefit in the less common subtypes. Thus far, the atypical mutations behave similarly in patients and in vitro. As in other studies, our two patients with insertion 20 mutation failed to respond to gefitinib (though one did have SD for 11 cycles) consistent with in vitro studies demonstrating that insertion 20 mutations are gefitinib insensitive.^13,34a The inclusion of patients with insertion 20 and other atypical mutations likely resulted in a lower ORR in our study compared with other trials accruing only patients with del 19 and L858R; however within the limited numbers of patients studied, this inclusion did not seem to adversely affect PFS or OS. Our study required patients sign consent for protocol treatment before molecular screening to increase the chance that mutation-positive patients ultimately receive primary gefitinib therapy. Ninety-one percent of our mutation-positive patients were treated, as opposed to 64% to 80% in the other studies, suggesting that our patients may be less selected or more representative of outcomes in general clinical practice. Finally, taken together, these studies demonstrate that the primary factor in determining efficacy of EGFR TKIs is tumor genomic make-up and not patient ethnicity, as similar results were observed across populations.

The prospective identification of the EGFR genotype and ongoing discoveries about TKI resistance allowed us to study why rare patients with activating EGFR mutations immediately progress on EGFR TKI therapy. We identified two patients harboring known activating EGFR mutations that also possessed known mechanisms of acquired TKI resistance at diagnosis. Both the exon 20 EGFR mutation T790M and MET amplification were initially described as acquired resistance mechanisms arising in mutation-positive patients after exposure to EGFR TKIs.^20-22 T790M has also been observed rarely in previously untreated patients with NSCLC, where similar to our case, both T790M and L858R were identified and subsequent gefitinib therapy was ineffective.^35,35a To our knowledge, this is the first report of an EGFR mutation-positive NSCLC instance with concurrent MET amplification and de novo clinical resistance to gefitinib. These instances illustrate that evaluating EGFR mutation–positive patients for potential concurrent resistance mechanisms before therapy may circumvent treatment with ineffective single-agent EGFR TKIs. Such patients might benefit from alternative regimens that effectively target specific resistance mechanisms (eg, concomitant EGFR and MET inhibition as shown by in vitro studies).²² Accordingly, we believe that as knowledge expands, genomically directed therapy will likely require multiple gene loci analyses using a multiplex high-throughput approach.

We also examined EGFR gene copy number by FISH, which has been associated with increased response and survival after EGFR TKI therapy.^29,36-38 Within our population of EGFR mutation–positive patients, FISH appeared to provide no additional clinical information, which is consistent with reports by other groups.^39,40

Despite the importance of our results, the findings should be interpreted in the context of some limitations. Our study used gefitinib, a drug no longer widely available in the United States after lack of survival benefit was reported in previously treated patients with nonselected NSCLC (though preplanned subgroup analyses revealed survival benefits in Asian and never-smoking patients).⁴¹ We designed our protocol before these results were known and chose gefitinib based on substantial data supporting its use in EGFR mutation–positive patients.^9,10,15,16 It is reassuring that similar results were obtained in the Spanish study with first-line erlotinib. Our study was also small (31 patients) and was subject to selection bias with a 1- to 3-week wait for molecular screening before eligibility could be confirmed. However, the primary limitation of our study was that without randomization we could not know whether a genotype-directed treatment strategy provides a survival advantage. EGFR mutations likely portend a more favorable biology and natural history regardless of therapy.^42-44 In an unplanned genetic subgroup analysis of the BR.21 trial, which randomly assigned patients previously treated with chemotherapy to erlotinib or placebo, there was no survival advantage in 15 patients with del 19 or L858R EGFR mutations treated with erlotinib compared with 19 mutation-positive patients on placebo (P = .12).^37,38 Notably, while 731 patients participated in BR.21, the EGFR mutation analysis was based on only 34 (4.7%). The apparent prolonged survival in our single-arm study clearly supports the need for ongoing prospective trials in genotype-defined populations comparing EGFR TKIs with standard chemotherapy.

In conclusion, first-line therapy with gefitinib in a molecularly defined population of patients with advanced NSCLC harboring EGFR mutations results in median PFS (9.2 months) and OS (17.5 months) that compare favorably with historical controls. Moreover, this novel approach was feasible with 35% of screened patients found to harbor mutations using simple clinical enhancement. This strategy has great potential to become a standard approach but further genotype-directed clinical trials are urgently needed.

	AUTHORS’ DISCLOSURES OF POTENTIAL CONFLICTS OF INTEREST

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Although all authors completed the disclosure declaration, the following author(s) indicated a financial or other interest that is relevant to the subject matter under consideration in this article. Certain relationships marked with a "U" are those for which no compensation was received; those relationships marked with a "C" were compensated. For a detailed description of the disclosure categories, or for more information about ASCO's conflict of interest policy, please refer to the Author Disclosure Declaration and the Disclosures of Potential Conflicts of Interest section in Information for Contributors.

Employment or Leadership Position: None Consultant or Advisory Role: Lecia V. Sequist, Genentech (C); Pasi A. Jänne, Roche (C), AstraZeneca (C); Jeffrey A. Engelman, Hoffman LaRoche (C); Bruce E. Johnson, Genzyme (C); Thomas J. Lynch, Genentech (C), OSI (C), Sanofi (C), Boerhinger-Ingelheim (C), Chugai (C), Lilly (C), Imclone (C), Bristol Myers Squibb (C), Xelixis (C), Pfizer (C) Stock Ownership: None Honoraria: David Spigel, AstraZeneca; Jeffrey A. Engelman, OSI Research Funding: Lecia V. Sequist, AstraZeneca; Renato G. Martins, AstraZeneca; David Spigel, AstraZeneca; Steven M. Grunberg, AstraZeneca; Alexander Spira, AstraZeneca; Pasi A. Jänne, AstraZeneca; Victoria A. Joshi, AstraZeneca; David McCollum, AstraZeneca; Tracey L. Evans, AstraZeneca; Alona Muzikansky, AstraZeneca; Georgiana L. Kuhlmann, AstraZeneca; Moon Han, AstraZeneca; Jonathan S. Goldberg, AstraZeneca; Jeffrey Settleman, AstraZeneca; A. John Iafrate, AstraZeneca; Jeffrey A. Engelman, AstraZeneca; Daniel A. Haber, AstraZeneca; Bruce E. Johnson, AstraZeneca; Thomas J. Lynch, AstraZeneca Expert Testimony: None Other Remuneration: Pasi A. Jänne, Genzyme; Daniel A. Haber, Genzyme; Bruce E. Johnson, Genzyme; Thomas J. Lynch, Genzyme

	AUTHOR CONTRIBUTIONS

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Conception and design: Lecia V. Sequist, Renato G. Martins, David Spigel, Pasi A. Jänne, Victoria A. Joshi, Tracey L. Evans, Alona Muzikansky, Jeffrey Settleman, A. John Iafrate, Jeffrey A. Engelman, Daniel A. Haber, Bruce E. Johnson, Thomas J. Lynch

Provision of study materials or patients: Lecia V. Sequist, Renato G. Martins, David Spigel, Steven M. Grunberg, Alexander Spira, Pasi A. Jänne, David McCollum, Tracey L. Evans, Jonathan S. Goldberg, Jeffrey A. Engelman, Bruce E. Johnson, Thomas J. Lynch

Collection and assembly of data: Lecia V. Sequist, Alexander Spira, Pasi A. Jänne, Victoria A. Joshi, Georgiana L. Kuhlmann, Moon Han, A. John Iafrate, Jeffrey A. Engelman

Data analysis and interpretation: Lecia V. Sequist, Pasi A. Jänne, Victoria A. Joshi, Alona Muzikansky, Georgiana L. Kuhlmann, Moon Han, A. John Iafrate, Jeffrey A. Engelman, Bruce E. Johnson, Thomas J. Lynch

Manuscript writing: Lecia V. Sequist, Alexander Spira, Pasi A. Jänne, A. John Iafrate, Jeffrey A. Engelman, Bruce E. Johnson, Thomas J. Lynch

Final approval of manuscript: Lecia V. Sequist, Renato G. Martins, David Spigel, Steven M. Grunberg, Alexander Spira, Pasi A. Jänne, Victoria A. Joshi, David McCollum, Tracey L. Evans, Alona Muzikansky, Jonathan S. Goldberg, Jeffrey Settleman, A. John Iafrate, Jeffrey A. Engelman, Daniel A. Haber, Bruce E. Johnson, Thomas J. Lynch

	Appendix

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	GLOSSARY

TOP ABSTRACT INTRODUCTION PATIENTS AND METHODS RESULTS DISCUSSION AUTHORS' DISCLOSURES OF... AUTHOR CONTRIBUTIONS Appendix GLOSSARY REFERENCES

 

EGFR (epidermal growth factor receptor):

Also known as HER-1, EGFR belongs to a family of receptors (HER-2, HER-3, HER-4 are other members of the family) and binds to the EGF, TGF-, and other related proteins, leading to the generation of proliferative and survival signals within the cell. It also belongs to the larger family of tyrosine kinase receptors and is generally overexpressed in several solid tumors of epithelial origin.

Tyrosine kinase inhibitors:

Molecules that inhibit the activity of tyrosine kinase receptors. They are small molecules developed to inhibit the binding of ATP to the cytoplasmic region of the receptor (eg, gefitinib), thus further blocking the cascade of reactions that is activated by the pathway.

Somatic mutation:

A change in the genotype of a cancer cell. This is distinguished from a germline mutation, which is a change in the genotype of all the normal cells in a patient's body. Germline mutations may be passed to offspring, but somatic mutations may not.

Amplification:

The increase of the copy number of a relatively narrow region of the genome, with the magnitude of the increase being large enough so that its generation requires more than a single aberrant event (eg, typically more than the gain of a single copy of the region.

PCR (polymerase chain reaction):

PCR is a method that allows logarithmic amplification of short DNA sequences within a longer DNA molecule.

MET:

The receptor for hepatocyte growth factor receptor, MET is a transmembrane receptor tyrosine kinase. The primary single chain precursor protein is post-translationally cleaved to produce the alpha and beta subunits; the mature receptor is composed of these subunits linked via disulfide bonds. Various mutations in the MET gene have been associated with papillary renal carcinoma.

FISH (fluorescence in situ hybridization):

In situ hydridization is a sensitive method that is generally used to detect specific gene sequences in tissue sections or cell preparations by hybridizing the complementary strand of a nucleotide probe to the sequence of interest. FISH uses a fluorescence probe to increase the sensitivity of in situ hybridization.

Genotype:

The specific genetic makeup of a given individual. Although genotypes give rise to the phenotype of an individual, genotypes and phenotypes are not always correlative. For example, some genotypes are expressed only under specific environmental conditions.

Gefitinib:

Belonging to the class of tyrosine kinase inhibitors, gefitinib (also known as Iressa) binds to the cytoplasmic region of the EGFR that also binds ATP. By competing with ATP binding that is essential for tyrosine phosphorylation, gefitinib inhibits activation of EGFR and blocks the cascade of reactions leading to cellular proliferation.

RECIST (Response Evaluation Criteria in Solid Tumors):

The Response Evaluation Criteria Group proposed amodel by which a combined assessment of all existing lesions, characterized by target lesions (to be measured) and nontarget lesions, is used to extrapolate an overall response to treatment.

	ACKNOWLEDGMENTS

 
The authors are indebted to the patients that participated in the study, the protocol staff at all the iTARGET institutions, particularly Elizabeth Kennedy and Patricia Ostler, and Elizabeth Lamont, MD, MS, for her assistance with graphics.

	NOTES

 
published online ahead of print at www.jco.org on May 5, 2008.

Supported by a research grant from AstraZeneca, study IRUSIRES0483.

Presented in part at the 43rd Annual Meeting of the American Society of Clinical Oncology, Chicago, IL, June 1-5, 2007.

Terms in blue are defined in the glossary, found at the end of this article and online at www.jco.org.

Authors’ disclosures of potential conflicts of interest and author contributions are found at the end of this article.

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Submitted October 12, 2007; accepted January 15, 2008.

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