Novel Agents in theTreatment of Lung Cancer : Advances in EGFR-Targeted Agents

As the literature about epidermal growth factor receptor (EGFR) mutations grows and screening for mutations becomes increasingly integrated into clinical care, it is important to examine how best to do somatic mutational analyses and how best to use the test results in clinical decision making. We began offering mutation screening by comprehensive direct sequence analysis of exons 18 to 24 of the tyrosine kinase domain of EGFR in August 2004 as part of clinical cancer care and protocol therapy at our institutions. All identified potential mutations are confirmed with three to five independent PCRs of the original genomic DNA sample and, if not previously noted in the literature, are compared with the patient’s germ-line DNA to ensure the finding is somatic. We formally analyzed the first 100 patients to undergo EGFR sequence analysis and found that testing was feasible and significantly affected the treatment of patients with non ^ small cell lung cancer (NSCLC). Patients harboring EGFR mutations were significantly more likely to receive recommendations for therapy with EGFR tyrosine kinase inhibitors (i.e., gefitinib or erlotinib) than patients without mutations. However, negative EGFR test results did not prevent physicians from administering these agents to selected patients. Ideally, a standardized technique for mutation testing could be developed, with demonstrated reproducibility and validity. Clinical trials incorporating molecular diagnostics are ongoing to assess the efficacy of EGFR tyrosine kinase inhibitors as first-line therapy for metastatic NSCLC and as adjuvant therapy for early-stage resected NSCLC. It is likely that mutation testing and other molecular analyses will be most useful in these two clinical situations. Agents that target the epidermal growth factor receptor (EGFR) have made a major impact on the treatment of advanced non–small cell lung cancer (NSCLC). The smallmolecule EGFR tyrosine kinase inhibitors (TKI) gefitinib and erlotinib elicit a dramatic response in some patients with relapsed NSCLC, with an objective response rate of 9% to 19% (1, 2). Patients previously treated with chemotherapy live longer when given erlotinib compared with those given placebo (3). Certain patient characteristics are associated with increased response to TKIs and may guide treatment decisions. These characteristics include adenocarcinoma tumor histology, female gender, nonsmoking history, and Asian race (1–5). Somatic activating mutations in the tyrosine kinase domain of EGFR also correlate with improved response (6–11) and, in some series, improved survival (12–15) with TKI therapy. Compared with wild-type EGFR, mutant receptors exhibit increased activation following ligand binding as well as enhanced inhibition by TKIs (16, 17). EGFR mutations are more common in patients with adenocarcinoma tumor histology, female gender, nonsmoking history, and Asian race, likely underlying the association of these clinical characteristics with treatment response. Due to increasing interest on the part of both clinicians and patients, we began offering mutation screening by comprehensive direct sequence analysis of exons 18 to 24 of EGFR as part of clinical cancer care and protocol therapy at our institutions in August 2004. More than 350 patients with NSCLC have been screened in the past year, with 23% of samples positive for EGFR mutations. Recently, we formally analyzed the first 100 patients to undergo EGFR testing to describe the feasibility of mutation testing in NSCLC clinical care, to characterize the patients referred for testing, and to evaluate the effect of mutation status on the clinical decisionmaking process. Novel Agents in theTreatment of Lung Cancer: Advances in EGFR-Targeted Agents Authors’ Affiliations: Cancer Center and Departments of Medicine and Pathology, Massachusetts General Hospital; Laboratory for Molecular Medicine, Harvard Medical School/Partners HealthCare Center for Genetics and Genomics; Department of Medical Oncology, Dana-Farber Cancer Institute; Departments of Medicine and Pathology, Brigham and Women’s Hospital; Department of Pathology, Harvard Medical School; and Broad Institute at Massachusetts Institute ofTechnology and Harvard, Boston, Massachusetts Received 1/15/06; revised 4/26/06; accepted 5/5/06. Presented at theThird Cambridge Conference on Novel Agents in theTreatment of Lung Cancer: Advances in EGFR-Targeted Agents, September 23-24, 2005, Cambridge, Massachusetts. Requests for reprints: Lecia V. Sequist, Massachusetts General Hospital Cancer Center, Yawkey Center for Outpatient Care, 32 Fruit Street, 7th Floor, Boston, MA 02114. Phone: 617-726-7812; Fax: 617-726-0453; E-mail: LVSequist@ Partners.org. F2006 American Association for Cancer Research. doi:10.1158/1078-0432.CCR-06-0099 www.aacrjournals.org Clin Cancer Res 2006;12(14 Suppl) July 15, 2006 4403s Research. on May 29, 2017. © 2006 American Association for Cancer clincancerres.aacrjournals.org Downloaded from Report of100 Patients Undergoing Clinical EGFR Testing We did a retrospective cohort analysis of the initial 100 NSCLC patients referred for somatic EGFR kinase domain sequencing at Massachusetts General Hospital (Boston, MA), Dana-Farber Cancer Institute (Boston, MA), and Brigham and Women’s Hospital (Boston, MA) from approximately August 2004 to February 2005. Clinicians could select which patients to refer for testing; however, patients needed to have sufficient tumor specimens available. Samples could be either paraffin-embedded or frozen tissue. Due to the low incidence of EGFR mutations in squamous cell tumors (18), patients with this diagnosis were not eligible for testing. Sequencing was done and interpreted at the Laboratory for Molecular Medicine of the Harvard Medical School/Partners HealthCare Center for Genetics and Genomics (Boston, MA; CLIA# 22D1005307). Patient age, gender, and race were collected from the electronic medical record system. Smoking status, cancer history, EGFR kinase domain sequencing results, and subsequent TKI treatment plans were documented using structured physician chart review. Former smokers were defined as having quit smoking at least 1 year before their diagnosis of NSCLC and never smokers were defined as having smoked <100 cigarettes in their lifetime. Pack-years of smoking were calculated by multiplying the number of packs smoked daily by the number of years of smoking. Tumor histology and EGFR kinase domain sequencing results were obtained from pathology reports. All pathology specimens were reviewed by pathologists at either Massachusetts General Hospital or Brigham and Women’s Hospital, and histology was categorized using the WHO classification system (19). This study was approved by our Institutional Review Board. Among the first 100 patients with NSCLC referred for somatic EGFR kinase domain sequencing as part of clinical cancer care, the mean age was 60.7 years and 63% were female. The majority of patients were white (76%) and had metastatic disease at the time the test was ordered (66%). Nearly all patients (94%) tested for EGFR mutations had adenocarcinoma, adenocarcinoma with bronchioloalveolar carcinoma features, or pure bronchioloalveolar carcinoma. Approximately one third of the patients were never smokers (29%). The average length of time from referral for testing to result availability was 12 business days. The majority of specimens submitted were paraffin embedded (74%). Six of the 74 (8%) paraffin-embedded specimens failed PCR amplification, whereas all of the 26 frozen specimens were successfully amplified. Among the 94 patients with interpretable results, 23 (24%) were found to have at least 1 mutation in the EGFR kinase domain, with 2 of these patients showing 2 point mutations each, for a total of 25 mutations identified. Among the 23 patients with mutations, 9 (39%) had one or more point mutations, including 5 (22%) with the substitution mutation 2573T>G (L858R), 12 (52%) had in-frame overlapping deletions in exon 19, and 2 (9%) had duplications in exon 20. As has been seen in other series, exon 19 deletions and the L858R point mutation in exon 21 accounted for the majority of mutations. No mutations were detected in exons 22, 23, or 24. In our sample, the only clinical characteristic that predicted mutations was smoking status. None of the 17 current smokers were found to have a mutation. Never smokers were significantly more likely to have an EGFR mutation than former smokers (odds ratio, 3.08; 95% confidence interval, 1.09-8.76). The mean number of pack-years smoked was significantly lower among EGFR mutation-positive patients (0.7 pack-years) compared with EGFR mutation-negative patients (25.0 pack-years; P < 0.001). For each additional pack-year smoked, there was a 4% decrease in the likelihood of having a mutation (odds ratio, 0.96; 95% confidence interval, 0.93-0.99). The number of pack-years of smoking remained a significant predictor of mutation status after controlling for gender, race, and tumor histology (odds ratio, 0.96; 95% confidence interval 0.93-0.99). Medical records of EGFR mutation-positive patients were significantly more likely to include documented plans to receive subsequent TKIs (83%) than EGFR mutation-negative patients (11%; P < 0.001). Clinicians documented that the EGFR results affected their prioritization of recommended therapies in 40% of all cases. Mutation status was more likely to change prioritization of treatment options in patients with metastatic disease (54%) than in local or locally advanced disease (19%; P = 0.002). Given this finding, we further analyzed the observed treatment patterns in patients with metastatic NSCLC (Fig. 1). Among the 31 patients with metastatic NSCLC whose test results affected treatment recommendations, 5 mutation-positive patients were offered first-line TKIs and 5 mutation-positive patients were offered second-line TKIs in lieu of chemotherapy. Twenty-one mutation-negative p