Allan R. Li

Novel D761Y and Common Secondary T790M Mutations in Epidermal Growth Factor Receptor–Mutant Lung Adenocarcinomas with Acquired Resistance to Kinase Inhibitors

Purpose: In patients whose lung adenocarcinomas harbor epidermal growth factor receptor (EGFR) tyrosine kinase domain mutations, acquired resistance to the tyrosine kinase inhibitors (TKI) gefitinib (Iressa) and erlotinib (Tarceva) has been associated with a second-site EGFR mutation, which leads to substitution of methionine for threonine at position 790 (T790M). We aimed to elucidate the frequency and nature of secondary EGFR mutations in patients with acquired resistance to TKI monotherapy. Experimental Design: Tumor cells from patients with acquired resistance were examined for secondary EGFR kinase domain mutations by molecular analyses. Results: Eight of 16 patients (50% observed rate; 95% confidence interval, 25-75%) had tumor cells with second-site EGFR mutations. Seven mutations were T790M and one was a novel D761Y mutation found in a brain metastasis. When combined with a drug-sensitive L858R mutation, the D761Y mutation modestly reduced the sensitivity of mutant EGFR to TKIs in both surrogate kinase and cell viability assays. In an autopsy case, the T790M mutation was found in multiple visceral metastases but not in a brain lesion. Conclusions: The T790M mutation is common in patients with acquired resistance. The limited spectrum of TKI-resistant mutations in EGFR, which binds to erlotinib in the active conformation, contrasts with a wider range of second-site mutations seen with acquired resistance to imatinib, which binds to ABL and KIT, respectively, in closed conformations. Collectively, our data suggest that the type and nature of kinase inhibitor resistance mutations may be influenced by both anatomic site and mode of binding to the kinase target.

Clinical Course of Patients with Non–Small Cell Lung Cancer and Epidermal Growth Factor Receptor Exon 19 and Exon 21 Mutations Treated with Gefitinib or Erlotinib

Purpose: In patients with non–small cell lung cancer (NSCLC), mutations in the epidermal growth factor receptor (EGFR) tyrosine kinase domain have been associated with sensitivity to erlotinib and gefitinib. We undertook this study to explore the relationship between EGFR mutation type and clinical variables, including treatment with gefitinib and erlotinib. Experimental Design: In patients with NSCLC, EGFR exon 19 deletion mutations and EGFR L858R point mutations were analyzed by nonsequencing PCR-based methods from paraffin blocks of tissue obtained before treatment. The results were correlated with clinical information (sex, pathologic subtype, race/ethnicity, treatment, and overall survival). Results: The two most common EGFR mutations were identified in 24% (70 of 291; 95% confidence interval, 26%-38%) of tumors from patients with NSCLC. EGFR mutation was associated with Asian ethnicity (P = 0.0023) and being a “never smoker” (P = 0.0001). Among patients with EGFR mutations, 39% (27 of 70) had EGFR L858R, whereas 61% (43 of 70) had an EGFR exon 19 deletion. After treatment with erlotinib (n = 12) or gefitinib (n = 22), patients with EGFR mutations had a median overall survival of 20 months. After treatment with erlotinib or gefitinib, patients with EGFR exon 19 deletions had significantly longer median survival than patients with EGFR L858R (34 versus 8 months; log-rank P = 0.01). Conclusions:EGFR mutations in exons 19 or 21 are correlated with clinical factors predictive of response to gefitinib and erlotinib. Those with EGFR exon 19 deletion mutations had a longer median survival than patients with EGFR L858R point mutation. These observations warrant confirmation in a prospective study and exploration of the biological mechanisms of the differences between the two major EGFR mutations.

Frequency and Distinctive Spectrum of KRAS Mutations in Never Smokers with Lung Adenocarcinoma

Purpose:KRAS mutations are found in ∼25% of lung adenocarcinomas in Western countries and, as a group, have been strongly associated with cigarette smoking. These mutations are predictive of poor prognosis in resected disease as well as resistance to treatment with erlotinib or gefitinib. Experimental Design: We determined the frequency and type of KRAS codon 12 and 13 mutations and characterized their association with cigarette smoking history in patients with lung adenocarcinomas. Results:KRAS mutational analysis was done on 482 lung adenocarcinomas, 81 (17%) of which were obtained from patients who had never smoked cigarettes. KRAS mutations were found in 15% (12 of 81; 95% confidence intervals, 8-24%) of tumors from never smokers. Similarly, 22% (69 of 316; 95% confidence intervals, 17-27%) of tumors from former smokers, and 25% (21 of 85; 95% confidence intervals, 16-35%) of tumors from current smokers had KRAS mutations. The frequency of KRAS mutation was not associated with age, gender, or smoking history. The number of pack years of cigarette smoking did not predict an increased likelihood of KRAS mutations. Never smokers were significantly more likely than former or current smokers to have a transition mutation (G→A) rather than the transversion mutations known to be smoking-related (G→T or G→C; P < 0.0001). Conclusions: Based on our data, KRAS mutations are not rare among never smokers with lung adenocarcinoma and such patients have a distinct KRAS mutation profile. The etiologic and biological heterogeneity of KRAS mutant lung adenocarcinomas is worthy of further study.

Molecular Characteristics of Bronchioloalveolar Carcinoma and Adenocarcinoma, Bronchioloalveolar Carcinoma Subtype, Predict Response to Erlotinib

PURPOSE We conducted this phase II trial to determine the efficacy of erlotinib in patients with bronchioloalveolar carcinoma (BAC) and adenocarcinoma, BAC subtype, and to determine molecular characteristics associated with response. PATIENTS AND METHODS Patients (n = 101) with BAC (n = 12) or adenocarcinoma, BAC subtype (n = 89), were enrolled. All patients received erlotinib 150 mg daily. Epidermal growth factor receptor (EGFR) mutation, EGFR copy number, EGFR immunohistochemistry (IHC), and KRAS mutation status were analyzed in available tumors. The primary end point was response rate (RR). RESULTS Overall RR was 22% (95% CI, 14% to 31%). In patients with pure BAC, the RR and median survival were 20% and 4 months, as compared with 23% and 19 months in those with adenocarcinoma, BAC subtype. No patient (zero of 18; 95% CI, 0% to 19%) whose tumor harbored a KRAS mutation responded to erlotinib. Patients with EGFR mutations had an 83% RR (15 of 18; 95% CI, 65% to 94%) and 23-month median OS. On univariate analysis, EGFR mutation and copy number were associated with RR and PFS. EGFR IHC was not associated with RR or progression-free survival (PFS). After multivariate analysis, only EGFR mutation was associated with RR and PFS. No molecular factors were associated with overall survival. CONCLUSION Erlotinib is active in BAC and adenocarcinoma, mixed subtype, BAC. Testing for EGFR and KRAS mutations can predict RR and PFS after treatment with erlotinib in this histologically enriched subset of patients with non-small-cell lung cancer (NSCLC). These data suggest that histologic subtype and molecular characteristics should be reported in clinical trials in NSCLC using EGFR-directed therapy.

EGFR gene amplification in breast cancer: correlation with epidermal growth factor receptor mRNA and protein expression and HER-2 status and absence of EGFR-activating mutations

The human epidermal growth factor receptor (HER) family of receptor tyrosine kinase has been extensively studied in breast cancer; however, systematic studies of EGFR gene amplification and protein overexpression in breast carcinoma are lacking. We studied EGFR gene amplification by chromogenic in situ hybridization (CISH) and protein expression by immunohistochemistry in 175 breast carcinomas, using tissue microarrays. Tumors with >5 EGFR gene copies per nucleus were interpreted as positive for gene amplification. Protein overexpression was scored according to standardized criteria originally developed for HER-2. EGFR mRNA levels, as measured by Affymetrix U133 Gene Chip microarray hybridization, were available in 63 of these tumors. HER-2 gene amplification by fluorescence in situ hybridization (FISH) and protein overexpression by immunohistochemistry were also studied. EGFR gene amplification (copy number range: 7–18; median: 12) was detected in 11/175 (6%) tumors, and protein overexpression was found in 13/175 (7%) tumors. Of the 11 tumors, 10 (91%) with gene amplification also showed EGFR protein overexpression (2+ or 3+ by immunohistochemistry). The EGFR mRNA level, based on Affymetrix U133 chip hybridization data, was increased relative to other breast cancer samples in three of the five tumors showing gene amplification. Exons 19 and 21 of EGFR, the sites of hotspot mutations in lung adenocarcinomas, were screened in the 11 EGFR-amplified tumors but no mutations were found. Three of these 11 tumors also showed HER-2 overexpression and gene amplification. Approximately 6% of breast carcinomas show EGFR amplification with EGFR protein overexpression and may be candidates for trials of EGFR-targeted antibodies or small inhibitory molecules.

Prognostic and therapeutic implications of EGFR and KRAS mutations in resected lung adenocarcinoma

Background: Somatic mutations in EGFR (exons 19 and 21) and KRAS (exon 2) are found in lung adenocarcinomas and have potential prognostic value in patients with advanced disease. These mutations also have therapeutic significance, as they predict for sensitivity and resistance, respectively, to EGFR tyrosine kinase inhibitor therapy. Whether EGFR and KRAS mutations also have an impact on survival in patients who undergo lung resection for curative intent in the absence of targeted therapy has not been established. Methods: We analyzed the clinical characteristics and outcomes data for 296 patients who underwent resection at our institution for stage I–III lung adenocarcinoma. Tumors were assessed for both EGFR and KRAS mutations by established methods. Results: EGFR and KRAS mutations were found in tumors from 40 (14%) and 50 (17%) patients, respectively. Patients with EGFR mutant tumors were more likely to be never smokers (48%), present with stage I disease (88%), and had a 90% (95% confidence interval [CI] 70–97%) 3-year overall survival, whereas patients with KRAS mutant tumors were more likely to be former/current smokers (92%), present with locally advanced disease (40%), and had a 66% (95% CI 48–79%) 3-year overall survival. Conclusions: EGFR and KRAS mutations define distinct molecular subsets of resected lung adenocarcinoma. Because EGFR and KRAS mutations also predict whether tumors are sensitive or resistant, respectively, to EGFR tyrosine kinase inhibitors, they can readily be used in clinical trials to help guide the administration of specific types of adjuvant therapy.

Epidermal growth factor receptor expression and gene amplification in colorectal carcinoma: An immunohistochemical and chromogenic in situ hybridization study

Recent data suggest that detection of epidermal growth factor receptor protein by immunohistochemistry (IHC) does not predict response to the antiepidermal growth factor receptor drug, cetuximab, in patients with colorectal carcinoma. In searching for foundation for further investigation to optimize patient selection for cetuximab therapy, this study sought to exploit the tissue microarray and chromogenic in situ hybridization techniques to evaluate the status of epidermal growth factor receptor gene amplification in colorectal cancer and its relationship with protein expression by IHC. The study included 158 primary or metastatic colorectal adenocarcinomas. Immunohistochemical results were scored as 0–3+ based on the intensity of membrane staining. The in situ hybridization signals were counted in 30 nuclei per tissue core. Overall, the rate of tissue loss was 7%, yielding 147 analyzable cases: 123 primary, 24 metastatic. Positive immunohistochemical staining of any intensity was detected in 85% (105/123) of primary and 79% (19/24) of metastatic tumors, whereas gene amplification (>5 gene copies/nucleus) was only seen in 12% (15/123) of primary and 8% (2/24) of metastatic tumors. Only 2/15 primary and 1/2 metastatic tumors that showed gene amplification were amplified at a high level (>10 gene copies/nucleus). Although a positive correlation was detected between the intensity of protein expression and the likelihood of gene amplification in both the primary (P=0.01) and the metastatic (P=0.05) tumors, IHC had a low specificity (17% in primary, 23% in metastatic) in predicting gene amplification. Conversely, all tumors that did not express the protein by IHC lacked gene amplification. Thus, this study shows that only a small fraction of epidermal growth factor receptor- positive colorectal carcinomas detected by IHC are associated with gene amplification. Additional studies are needed to determine whether epidermal growth factor receptor gene amplification bears any informative value in predicting response to cetuximab-based therapy.

EGFR Mutations in Lung Adenocarcinomas: Clinical Testing Experience and Relationship to EGFR Gene Copy Number and Immunohistochemical Expression

Lung adenocarcinomas responsive to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors possess EGFR mutations and often increased EGFR copy number. We prospectively studied 334 clinical cases using polymerase chain reaction-based assays to detect deletions within exon 19 and the L858R mutation in exon 21, which together account for approximately 90% of EGFR mutations. Seventy-eight (23%) of these tumors had an EGFR mutation, with 55 (71%) exon 19 deletions and 23 (29%) exon 21 L858R mutations. We were able to compare mutant and normal EGFR alleles and found a preferential amplification of the mutant allele. The association of mutations with EGFR amplification (determined by chromogenic in situ hybridization) and EGFR expression (determined by immunohistochemistry) was further examined in a subset of 60 tumors. EGFR amplification (> or =5 EGFR signals per nucleus) was seen in 15 of 29 (52%) EGFR-mutated tumors but in only five of 31 (6%) non-mutated tumors (P = 0.006). EGFR overexpression was strongly associated with amplification but was statistically independent of EGFR mutation. Most patients with EGFR mutations (17 of 29, 59%) never smoked compared with 13% (four of 31) of patients lacking such mutations (P = 0.0003). The association of amplification with smoking status was marginal and was nonexistent with EGFR expression. Thus, these results indicate that EGFR amplification, preferentially of the mutant allele, often accompanies EGFR mutation, whereas EGFR immunohistochemical staining associates with amplification but cannot predict EGFR mutation status.

Clinical testing experience and relationship to EGFR gene copy number and immunohistochemical expression

Lung adenocarcinomas responsive to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors possess EGFR mutations and often increased EGFR copy number. We prospectively studied 334 clinical cases using polymerase chain reaction-based assays to detect deletions within exon 19 and the L858R mutation in exon 21, which together account for approximately 90% of EGFR mutations. Seventy-eight (23%) of these tumors had an EGFR mutation, with 55 (71%) exon 19 deletions and 23 (29%) exon 21 L858R mutations. We were able to compare mutant and normal EGFR alleles and found a preferential amplification of the mutant allele. The association of mutations with EGFR amplification (determined by chromogenic in situ hybridization) and EGFR expression (determined by immunohistochemistry) was further examined in a subset of 60 tumors. EGFR amplification (> or =5 EGFR signals per nucleus) was seen in 15 of 29 (52%) EGFR-mutated tumors but in only five of 31 (6%) non-mutated tumors (P = 0.006). EGFR overexpression was strongly associated with amplification but was statistically independent of EGFR mutation. Most patients with EGFR mutations (17 of 29, 59%) never smoked compared with 13% (four of 31) of patients lacking such mutations (P = 0.0003). The association of amplification with smoking status was marginal and was nonexistent with EGFR expression. Thus, these results indicate that EGFR amplification, preferentially of the mutant allele, often accompanies EGFR mutation, whereas EGFR immunohistochemical staining associates with amplification but cannot predict EGFR mutation status.

EGFR Mutations in Lung Adenocarcinomas

Lung adenocarcinomas responsive to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors possess EGFR mutations and often increased EGFR copy number. We prospectively studied 334 clinical cases using polymerase chain reaction-based assays to detect deletions within exon 19 and the L858R mutation in exon 21, which together account for approximately 90% of EGFR mutations. Seventy-eight (23%) of these tumors had an EGFR mutation, with 55 (71%) exon 19 deletions and 23 (29%) exon 21 L858R mutations. We were able to compare mutant and normal EGFR alleles and found a preferential amplification of the mutant allele. The association of mutations with EGFR amplification (determined by chromogenic in situ hybridization) and EGFR expression (determined by immunohistochemistry) was further examined in a subset of 60 tumors. EGFR amplification (> or =5 EGFR signals per nucleus) was seen in 15 of 29 (52%) EGFR-mutated tumors but in only five of 31 (6%) non-mutated tumors (P = 0.006). EGFR overexpression was strongly associated with amplification but was statistically independent of EGFR mutation. Most patients with EGFR mutations (17 of 29, 59%) never smoked compared with 13% (four of 31) of patients lacking such mutations (P = 0.0003). The association of amplification with smoking status was marginal and was nonexistent with EGFR expression. Thus, these results indicate that EGFR amplification, preferentially of the mutant allele, often accompanies EGFR mutation, whereas EGFR immunohistochemical staining associates with amplification but cannot predict EGFR mutation status.