Possible differential EGFR-TKI efficacy among exon 19 deletional locations in EGFR-mutant non-small cell lung cancer

First-line Osimertinib for Lung Cancer With Uncommon EGFR Exon 19 Mutations and EGFR Compound Mutations

Introduction

Up to 20% of EGFR-mutated NSCLC cases harbor uncommon EGFR mutations, including atypical exon 19 and compound mutations. Relatively little is known about the efficacy of osimertinib in these cases.

Methods

Patients treated with first-line osimertinib for NSCLC with rare EGFR exon 19 (non E746_A750del) or compound mutations were included. Response assessment and time to progression were determined using Response Evaluation Criteria in Solid Tumors version 1.1 criteria. Kaplan-Meier analyses were used to estimate progression-free survival (PFS), time to treatment discontinuation (TTD), and overall survival (OS).

Results

Thirty-seven patients with NSCLC harboring an atypical EGFR exon 19 mutation or compound mutation were treated with first-line osimertinib at Johns Hopkins from 2016 to 2021. Overall response rate (ORR) was 76% and median PFS, TTD, and OS were 13 months (95% confidence interval [CI]: 10-15), 22 months (95% CI: 17-32) and 36 months (95% CI, 29-48), respectively. Among atypical exon 19 mutations (n = 25), ORR was 80%, median PFS was 12 months (95% CI: 10-15), median TTD was 19 months (95% CI: 17-38), and median OS was 48 months (95% CI: 25-not reached). Compound mutations (n = 12) had an ORR of 67%, median PFS of 14 months (95% CI: 5-22), median TTD of 26 months (95% CI: 5-36), and median OS of 36 months (95% CI: 20-46). Twelve patients (32%) continued first-line osimertinib after local therapy for oligoprogression.

Conclusions

Osimertinib exhibited favorable outcomes for rare EGFR exon 19 and compound mutations. The heterogeneity in outcomes among these groups of tumors with similar mutations underscores the need for continued reporting and further study of outcomes among rare variants to optimize management for each patient.

RELAY, Erlotinib Plus Ramucirumab in Untreated, EGFR-Mutated, Metastatic NSCLC: Outcomes by EGFR Exon 19 Deletion Variants

Introduction

EGFR gene mutations are drivers of NSCLC. The RELAY double-blind, placebo (PBO)-controlled phase 3 study revealed superior progression-free survival (PFS) for ramucirumab plus erlotinib (RAM + ERL) versus PBO (PBO + ERL) in patients with untreated advanced NSCLC and an EGFR-activating mutation. This exploratory analysis evaluated potential associations between EGFR exon 19 deletion (ex19del) variants and clinical outcomes.

Methods

Patients (N = 449) were randomized (1:1) to RAM plus ERL or PBO plus ERL. Plasma samples were collected at baseline, on treatment, and at 30-day post-study treatment discontinuation follow-up. Baseline and treatment-emergent gene alterations were investigated by Guardant360 next-generation sequencing. Patients with a valid baseline plasma sample and ex19del were included (RAM + ERL, n = 62; PBO + ERL, n = 72).

Results

The most common ex19del variant was E746_A750del (67.2%); EGFR E746 deletions (E746del) occurred more frequently than L747 deletions (74.6% versus 25.4%, respectively). TP53 mutations were the most frequently co-occurring baseline gene alterations. With treatment arms combined, median PFS was 18.0 months versus 12.5 months for patients with uncommon (non-E746_A750del, n = 44) versus common (E746_A750del, n = 90) ex19del variants (hazard ratio [HR] = 1.657 [95% confidence interval or CI:1.044-2.630]). Median PFS was longer with RAM plus ERL versus PBO plus ERL for patients with the common (15.2 versus 9.9 mo; HR = 0.564 [95% CI: 0.344-0.926]) and E746del (15.4 versus 9.9 mo; HR = 0.587 [95% CI: 0.363-0.951]) variants. Treatment-emergent post-progression EGFR T790M rates were higher in the common versus uncommon and E746del versus L747 deletion subgroups.

Conclusions

RAM plus ERL provides benefit and improves treatment outcomes for patients with metastatic NSCLC with EGFR ex19del variants.

Efficacy of Osimertinib in Patients with Lung Cancer Positive for Uncommon EGFR Exon 19 Deletion Mutations

PURPOSE

The uncommon EGFR exon 19 deletion (ex19del), L747_A750>P, demonstrates reduced sensitivity to osimertinib compared with the common ex19del, E746_A750del in preclinical models. The clinical efficacy of osimertinib in patients with non-small cell lung cancer harboring L747_A750>P and other uncommon ex19dels is not known.

EXPERIMENTAL DESIGN

The AACR GENIE database was interrogated to characterize the frequency of individual ex19dels relative to other variants, and a multicenter retrospective cohort was used to compare clinical outcomes for patients with tumors harboring E746_A750del, L747_A750>P, and other uncommon ex19dels who received osimertinib in the first line (1L) or in second or later lines of therapy and were T790M+ (≥2L).

RESULTS

ex19dels comprised 45% of EGFR mutations, with 72 distinct variants ranging in frequency from 28.1% (E746_A750del) to 0.03%, with L747_A750>P representing 1.8% of the EGFR mutant cohort. In our multi-institutional cohort (N = 200), E746_A750del was associated with significantly prolonged progression-free survival (PFS) with 1L osimertinib versus L747_A750>P [median 21.3 months (95% confidence interval, 17.0-31.7) vs. 11.7 months (10.8-29.4); adjusted HR 0.52 (0.28-0.98); P = 0.043]. Osimertinib efficacy in patients with other uncommon ex19dels varied on the basis of the specific mutation present.

CONCLUSIONS

The ex19del L747_A750>P is associated with inferior PFS compared with the common E746_A750del mutation in patients treated with 1L osimertinib. Understanding differences in osimertinib efficacy among EGFR ex19del subtypes could alter management of these patients in the future.

Different treatment efficacies and T790M acquisition of EGFR-TKIs on NSCLC patients with variable Del-19 subtypes of EGFR

EGFR exon 19 deletion (Del-19) comprises multiple advanced NSCLC subtypes. EGFR-tyrosine kinase inhibitor (TKI) efficacy and T790M acquisition in various Del-19 subtypes is unknown. We prospectively collected tissue samples from patients harboring NSCLC with Del-19 between 2006 and 2020. We evaluated EGFR-TKI treatment effectiveness among the different Del-19 subtypes. We collected 1391 NSCLC samples from 892 patients with Del-19, and the most common subtype was del E746-A750 (67.5%). 741 patients had taken first- or second-generation EGFR-TKIs. There were no significant differences in response rates between patients with different Del-19 subtypes (P = .630). Patients with indel E746 had the longest median PFS (14.6 months), but those with non-LRE deletions had the shortest PFS (8.9 months; P = .002). For OS analysis, patients with indel E746 also had the longest OS (34.1 months), but those with non-LRE deletions had the shortest OS (21.1 months; P = .046). Patients with different Del-19 subtypes showed no significant differences in the T790M acquisition rates (P = .443). Among the 151 patients with acquired T790M who received third-generation EGFR-TKIs, the Del-19 subtype was not associated with different RR and PFS. In vitro cellular viability and activation of the EGFR pathway analysis were consistent with the clinical findings. In conclusion, compared with del E746-A750, indel E746 was associated with longer PFS and OS, but the non-LRE subtype was correlated with shorter survival prognosis. There were no significant differences in the acquired T790M rate and treatment effectiveness of subsequent third-generation EGFR-TKIs between various Del-19 subgroups.

Heterogeneous Response to First-Generation Tyrosine Kinase Inhibitors in Non-Small-Cell Lung Cancers with Different EGFR Exon 19 Mutations

BACKGROUND

Epidermal growth factor receptor (EGFR) exon 19 deletions (19dels) appear in a large number of variants, which has not been distinguished in previously published trials despite differences in deletion and insertion locations.

OBJECTIVE

The aim of this study was to investigate the therapeutic response of patients with different EGFR exon 19dels to first-generation tyrosine kinase inhibitors (TKIs) and the mechanisms by which their tumors acquire resistance to these TKIs.

PATIENTS AND METHODS

The clinical outcomes of 195 patients harboring EGFR exon 19dels and receiving first-generation EGFR TKIs between July 2011 and June 2019 were retrospectively analyzed.

RESULTS

A total of twenty EGFR exon 19dels variants were identified. The patients were divided into three groups according to the first residue of the deletion, including E746, L747, and other residues (T751 or S752). The median progression-free survival (PFS) of patients treated with EGFR TKIs was significantly different between groups (p < 0.001). Patients harboring EGFR exon 19dels starting at T751 or S752 had the shortest median PFS (2.9 months), followed by those with E746 (11.4 months) and those with L747 (17.2 months). Analyzing 140 patients who had progressed on therapy, EGFR exon 19dels beginning at T751 or S752 were associated with a low incidence of the T790M mutation (16.7%).

CONCLUSIONS

Deletion location and type variants (with or without an insertion and/or a substitution) might affect first-generation TKI efficacy, and different EGFR exon 19dels should be considered when making decisions on which EGFR TKI should be used.

The impact of EGFR exon 19 deletion subtypes on clinical outcomes in non-small cell lung cancer

Background

The study investigated the resistant pattern and clinical outcomes of epidermal growth factor receptor (EGFR) exon 19 deletion (19del) subtypes to tyrosine kinase inhibitors (TKIs) in non-small cell lung cancer (NSCLC).

Methods

Two hundred eight treatment naive NSCLC patients detected as EGFR 19del using amplification-refractory mutation system (ARMS) were included. DNA sequencing was used to detect the subtypes. Clinicopathological features as well as patients’ outcomes treated with first-line EGFR-TKIs were analyzed.

Results

Thirteen EGFR 19del subtypes were confirmed in 181 samples (87.0%). Among these, delE746_A750 was the most frequent subtype (130/181, 71.8%). delE746_A750 and deletions starting from E746 were frequently found in female (P=0.003 and P=0.013, respectively) and never smokers (P=0.002 and P=0.014, respectively) than non-delE746_A750 and deletions starting from L747 patients, respectively. T790M was more frequently occurred in delE746_A750 than non-delE746_A750 (P=0.001) and deletions starting from E746 than L747 patients (P=0.006) after first-line EGFR-TKIs resistance. Patients harboring deletions starting from L747 with insertions had significantly shorter progression-free survival (PFS) than deletions starting from L747 without insertion (8.3 vs. 15.0 m, P=0.017), or all other patients (8.3 vs. 12.6 m, P=0.027). Different 19del subtypes with T790M mutation had similar PFS when treated with osimertinib (P=0.102).

Conclusions

Patients with EGFR 19del subtypes had different clinicopathological features, and resistant pattern when treated with first-line TKIs. Patients harboring deletions starting from L747 with insertions had inferior outcomes than other subtypes.

EGFR mutation genotypes affect efficacy and resistance mechanisms of osimertinib in T790M-positive NSCLC patients

Background

Osimertinib is a potent third-generation EGFR tyrosine kinase inhibitor (TKI) with robust activity in advanced EGFR-mutant non-small cell lung cancer (NSCLC), including those with T790M resistance mutation. However, a broad interpatient variability was observed. This study aimed to evaluate whether EGFR-mutant genotypes affect the clinical outcomes and resistance mechanisms in T790M-positive NSCLC patients receiving osimertinib therapy.

Methods

All NSCLC patients treated with osimertinib in our institute were screened. We included those with known EGFR-mutant genotypes and T790M positivity. Clinical outcomes including objective response rate (ORR), clinical benefit rate (CBR), progression-free survival (PFS), and overall survival (OS), were evaluated and compared between different EGFR genotypes. Patients with next-generation sequencing testing or tumor rebiopsy after osimertinib treatment were analyzed for resistance mechanisms.

Results

ORR, CBR, PFS, and OS were all non-significantly different among patients harboring EGFR exon 19 deletion (19Del, n=136), L858R (n=93), and uncommon mutations (n=6). However, a subset of tumors with deletion starting at E746 (ΔE746, n=98), but not non-ΔE746 tumors (n=38), had better clinical outcomes than L858R tumors (n=93). Frequencies of T790M loss and C797S acquisition after osimertinib treatment were similar between 19Del (n=56) and L858R tumors (n=33). However, compared with L858R tumors (n=33), those with 19Del ΔE746 subtype (n=40) had a higher whereas non-ΔE746 subtype (n=16) had a similar frequency of acquired C797S mutation. Combined analysis of our cohort and public cohort confirmed these findings.

Conclusions

Our findings indicate that the EGFR 19Del subtypes affect the clinical outcomes and resistance mechanisms to osimertinib in T790M-positive patients. Identifying patients with relatively worse treatment outcomes may be informative for establishing new therapies for these patients.

The significance of epidermal growth factor receptor uncommon mutations in non-small cell lung cancer: A systematic review and critical appraisal

Uncommon epidermal growth factor receptor (EGFR) mutations collectively account for 10% of EGFR mutations, harboring heterogeneous molecular alterations within exons 18-21 with clinically variable responses to EGFR tyrosine kinase inhibitors (TKIs) in advanced Non-Small Cell Lung Cancer (NSCLC) patients. In addition, with the introduction of different NGS gene approach an improvement of EGFR mutations detection was reported. Today, no specific studies have prospectively evaluated uncommon sensitizing mutations in detail and no firm standard of care has been established in the first-line setting. The aim of this comprehensive review is to critically consider the clinical role of uncommon EGFR mutations highlighting the results of several in vitro and in vivo studies, which singly evaluated the sensitivity of uncommon mutations to currently European of Medicines Agency (EMA)-approved EGFR TKIs in cell lines, xenograft models and humans, in order to obtain a practical guide for refining the clinical decision-making process.

Differential significance of molecular subtypes which were classified into EGFR exon 19 deletion on the first line afatinib monotherapy

BACKGROUND

Epidermal growth factor receptor (EGFR)-sensitizing mutation, exon 19 deletion consists of several molecular variants. Influences of these variants on clinical response to EGFR tyrosine kinase inhibitors remain elusive.

METHODS

West Japan Oncology Group 8114LTR is a prospective, multi-institutional biomarker study. Treatment naïve, advanced non-small-cell lung cancer patients with EGFR-sensitizing mutation received afatinib monotherapy. We conducted a preplanned subset analysis of patients harboring exon 19 deletion. Tumor tissue exon 19 deletion molecular variants were identified by blocking-oligo-dependent polymerase chain reaction (PCR) and by Luminex Technology. Plasma cfDNA was also obtained before and after the treatment and EGFR mutations were detected with multiplexed, pico-droplet digital PCR assay.

RESULTS

Among 57 registered patients, twenty-nine patients were exon 19 deletion. Tissue DNA and cfDNA were available in 26 patients. Among the detected seven molecular variants, the most frequent was p.E746_A750delELREA (65.4%). According to the various classifications of molecular variants, twenty one (80.8%) were classified into 15-nucleotide deletion, one (3.8%) into 18-nucleotide deletion, and four patients (15.4%) into other insertion/substitution variant subgroups. The patient subgroup with 15-nucleotide deletion showed significantly longer progression-free survival than patients in other mixed insertion/substitution variant subgroup (p = 0.0244).

CONCLUSIONS

The clinical significance of molecular variants of exon 19 deletion on the first line afatinib monotherapy is reported here for the first time. Further investigation is needed for development of better therapeutic strategies.

TRIAL REGISTRATION

This trial was registered at UMIN Clinical Trials Registry at 2014/12/4 (UMIN000015847).

Molecular characteristics and clinical outcomes of EGFR exon 19 indel subtypes to EGFR TKIs in NSCLC patients

Patients with non-small cell lung cancer (NSCLC) with activating epidermal growth factor receptor (EGFR) mutations (exon 19 deletions and L858R) benefit from EGFR tyrosine kinase inhibitors (TKIs). However, some researchers have reported that responses to TKIs differ by subtypes of EGFR exon 19 mutations. We retrospectively analyzed EGFR exon 19 deletion subtypes and their correlation with clinical outcomes of treatment with TKIs. A cohort of 2664 consecutive patients with NSCLC was enrolled. A total of 440 EGFR exon 19 deletions were defined as 39 subtypes. Among them, 158 patients with advanced lung adenocarcinoma with EGFR exon 19 deletion mutations received EGFR-TKIs. There were no significant differences in progression-free survival or overall survival among patients with non-LRE deletions, delE746, or delL747 (P = 0.463 and P = 0.464, respectively). Furthermore, two patients with EGFR exon19 insertion had durable response to EGFR-TKIs. In conclusion, EGFR exon 19 is highly fragile, resulting in many different deletion and insertion subtypes. There were no significant differences in clinical outcomes after TKI treatment across the different subtypes. It is necessary to attempt to identify all patients with exon 19 deletions so that they can be offered TKI treatment.

EGFR with TKI-sensitive mutations in exon 19 is highly expressed and frequently detected in Chinese patients with lung squamous carcinoma

Recently, tyrosine kinase inhibitors (TKIs) have been recommended as a first-line treatment for advanced non-small cell lung cancer (NSCLC), significantly improving the treatment outcomes of lung adenocarcinoma patients with the EGFR mutation. However, the application of TKIs for lung squamous cell carcinoma (SCC), the second largest pathological subtype of NSCLC, remains controversial because available data for the EGFR mutation profile and frequency in SCC patients are limited. In this study, 89 bronchoscopic-biopsy specimens from Chinese SCC male patients were assayed for EGFR exon 19 mutation, using improved polymerase chain reaction-denature gel gradient electrophoresis. EGFR exon 19 mutations were detected in 77 of 89 (86.5%) patients, and included six kinds of point mutations (11.6%) and two deletions (Del_747-751 [64.9%] and Del_746-751 [23.3%]). We found that the proportion of mutated EGFR varied from 0.98% to 100% in positive specimens and increased with the development of the disease. The difference of proportion between Stage IV patients and Stage II patients or Stage III patients was significant (P<0.001). These results provided valuable clues to explain the reason why patients harboring the same mutation responded distinctly to TKI treatment. Del_747-751 and Del_746-751 were the dominant mutations in the assayed SCC patients (76.4%), and both belong to the EGFR-TKI-sensitive mutation. Recently research demonstrated that Del_746-751 patients have better response to EGFR-TKI than Del_L747-751 patients. However, our study indicated that majority of SCC patients (55.5%) carried Del_ L747-751. We suggest that the unique clinic features of SCC should be further studied to reveal the mechanism of poorer treatment outcome of EGFR-TKI therapy, and that a better treatment plan and more specific, potent targeted drugs for lung SCC need to be developed.

Factors associated with efficacy of first-generation epidermal growth factor receptor tyrosine kinase inhibitors in non-small-cell lung cancer

The finding of epidermal growth factor receptor tyrosine kinase inhibitors, which reflects a classical process of translational research, is a critical milestone for non-small-cell lung cancer treatment. Currently, epidermal growth factor receptor tyrosine kinase inhibitors are recommended as first-line therapy for non-small-cell lung cancer patients harboring epidermal growth factor receptor-sensitive mutations. The status of epidermal growth factor receptor mutation is widely acknowledged as superior to other clinical factors, such as smoking, gender, and histological types for predicting the response to epidermal growth factor receptor tyrosine kinase inhibitors. However, recent studies have shown that the efficacy might differ in patients with the same epidermal growth factor receptor-sensitive mutations, highlighting the need to investigate the putative factors related to the efficacy of epidermal growth factor receptor tyrosine kinase inhibitors. This article reviews the factors associated with clinical efficacy of first-generation epidermal growth factor receptor tyrosine kinase inhibitors, such as gefitinib and erlotinib, and analyzes their potential implications with respect to clinical application. In addition, new findings related to clinical practice with respect to epidermal growth factor receptor tyrosine kinase inhibitors efficacy were summarized in this article.

EGFR Mutation Subtypes Influence Survival Outcomes following First-Line Gefitinib Therapy in Advanced Asian NSCLC Patients

INTRODUCTION

Activating mutations in the EGFR gene have been shown to confer sensitivity to EGFR tyrosine kinase inhibitors in patients with advanced NSCLC. However, wide interpatient variability in treatment outcomes in response to EGFR tyrosine kinase inhibitors in these patients remains unaccounted for. This study aimed to evaluate the influence of EGFR mutation types and subtypes on survival outcomes in advanced Asian patients with NSCLC receiving first-line gefitinib therapy.

METHODS

Patients with stage IIIB or IV NSCLC who were harboring EGFR mutations, receiving first-line gefitinib treatment, and of Asian descent (N = 383) were evaluated. Overall survival (OS) and progression-free survival (PFS) were estimated by Kaplan-Meier analysis. Log-rank tests and Cox proportional hazards models were implemented to evaluate the differences in PFS and OS.

RESULTS

Significant differences in PFS were observed between patients carrying EGFR mutations in exons 18, 19, 20, and 21, with patients carrying EGFR exon 19 mutations having the longest median PFS (overall p = 8.88 × 10^-15). Comparison of PFS among the five different exon 19 mutation subtypes and among the two exon 19 deletion start codons did not reveal any significant differences. No significant difference was observed in OS among patients carrying EGFR mutations on different exons (overall p = 0.054); however, OS was found to be significantly different among the various subtypes of exon 19 mutations, with the 15-nucleotide deletion "non-ELREA" group having the shortest OS of 11.3 months (overall p = 0.025).

CONCLUSIONS

EGFR mutation types and subtypes significantly influence survival outcomes in patients with advanced NSCLC who are receiving first-line gefitinib treatment.

Not all epidermal growth factor receptor mutations in lung cancer are created equal: Perspectives for individualized treatment strategy

Somatic mutations in the epidermal growth factor receptor (EGFR) gene are present in approximately 20% (in Caucasians) to 40% (in East Asians) of adenocarcinomas of the lung. Targeted therapy for these lung cancers has been established based on evidence regarding mainly common mutations; that is, exon 19 deletions (Del19) and L858R. EGFR‐tyrosine kinase inhibitors (TKI), gefitinib, erlotinib or afatinib showed high objective response rates (ORR) of approximately 60%. Several studies suggested that Del19 might be more sensitive to EGFR‐TKI than L858R. On the other hand, it has been difficult to establish evidence for other less common mutations, accounting for 12% of all EGFR mutations, because there are many variants and many studies have excluded patients with these uncommon mutations. However, recent studies revealed that these rare genotypes could be targetable if appropriate TKI are selected. For example, G719X (X denotes A, S, C and so on), Del18, E709K, insertions in exon 19 (Ins19), S768I or L861Q showed moderate sensitivities to gefitinib or erlotinb with ORR of 30%–50%. However, afatinib appeared to be especially effective for these tumors. Although Ins20s (except for insFQEA) have been regarded as resistant mutations, osimertinib may be effective for rare subtypes of them and nazartinib (EGF816) is promising for the majority of them. For the further development of targeted therapy in all EGFR mutations, it is important to precisely detect targetable mutations, to select the most appropriate TKI for each mutation, and to continue investigating in vitro studies and collecting clinical data on even rare mutations.

Correlation of EGFR Del 19 with Fn14/JAK/STAT signaling molecules in non-small cell lung cancer

Previous research has shown that p-EGFR (particularly mutated EGFR) may activate fibroblast growth factor-inducible 14 (Fn14) expression in non-small cell lung cancer (NSCLC), and the JAK/STAT signaling pathway may participate in this process. Thus, in order to verify this hypothesis, correlations among the expression levels of EGFR Del 19, Fn14 and JAK/STAT were detected and analyzed. The expression and location of these molecules were assessed using IHC, immunohistofluorescence, RT-qPCR and western blotting. The differences and correlations in the expression of these molecules and clinical pathological characteristics were statistically analyzed using Mann-Whitney U, Kruskal‑Wallis H and cross-table tests. Kaplan-Meier survival analysis and Cox proportional hazards models were used to estimate the effect of EGFR Del 19 and Fn14 expression on survival. Data showed that EGFR Del 19, Fn14 and JAK1/STAT1 expression was significantly related with differentiation, pTNM stage and lymphatic metastasis (P<0.01) and there was a marked correlation of EGFR Del 19, Fn14 and JAK1/STAT1 expression with histological type, differentiation, pTNM stage of NSCLC (P<0.05; rs>0.3). Immunohistofluorescence showed that there was a co-localization phenomenon between EGFR Del 19 and Fn14 expression. NSCLC patients with higher EGFR Del 19/Fn14 expression had a significantly worse prognosis than those with lower EGFR Del 19/Fn14 expression (P=0.0155/P=0.001; log-rank test). The multivariate analysis indicated that Fn14 expression may be an independent prognostic factor in NSCLC with EGFR Del 19 [hazard ratio (HR), 0.326; P=0.042]. Therefore, our results indicate that EGFR Del 19 may promote Fn14 and JAK1/STAT1 expression in NSCLC and Fn14 may serve as a prognostic biomarker in NSCLC with EGFR Del 19.

Analysis of a single-codon E746 deletion in exon 19 of the epidermal growth factor receptor

PURPOSE

Epidermal growth factor receptor (EGFR) gene mutations are the most established genomic biomarkers for the efficacy of EGFR tyrosine kinase inhibitors (EGFR-TKIs). The most frequent deletion in exon 19 is delE746_750, followed by del747_753insS and del747_750insP. Since investigations of delE746 have not been reported previously, it is unclear if delE746 conveys sensitivity to TKI effect of TKI on EGFR delE746. The objective was to characterize delE746 of the EGFR gene and to explore the effects of TKIs on the delE746.

METHODS

We assessed the ability of gefitinib to inhibit phosphorylation of clonal L929 cell lines expressing EGFR with delE746. 3-D structures of the EGFR proteins were also used to investigate the interaction with gefitinib.

RESULTS

The delE746 mutant EGFR-expressing cells exhibited gefitinib-sensitive autophosphorylation, which altered the structure of the EGFR and increased the instances of docking during docking simulations of gefitinib with the EGFR-TK. This mutant revealed that it exhibited molecular conformation alterations, and more frequent binding with gefitinib compared to wild-type EGFR. We administered EGFR-TKI, gefitinib to a Japanese woman with lung cancer that contained delE746. The patient achieved partial response after a 5 month of treatment with gefitinib.

CONCLUSION

Our study revealed biological, structural, and probably clinical features of the delE746 form of EGFR.

Frequent BRAF or EGFR Mutations in Ciliated Muconodular Papillary Tumors of the Lung

INTRODUCTION

Ciliated muconodular papillary tumors (CMPTs) are recently characterized, rare peripheral nodules of the lung. These small tumors are histologically comprised of a vaguely organized mixture of nonatypical ciliated columnar cells, mucous cells, and basal cells, and consistently follow a benign clinical course. However, the histogenesis of CMPTs remains uncertain.

METHODS

We performed detailed genomic analyses of 10 archived CMPT cases, using next-generation sequencing and high-resolution melting analysis.

RESULTS

Mutations were identified in eight of the 10 cases (80%); four cases harbored the BRAF-V600E mutation, one case harbored the BRAF-G606R mutation, and three cases harbored deletions in exon 19 of EGFR. All of the deletions in EGFR were of the E746-T751/S752V subtype.

CONCLUSIONS

The high prevalence of driver gene mutations in CMPTs supports the notion that these lesions are neoplastic rather than reactive or metaplastic.

Correlations Between the EGFR Mutation Status and Clinicopathological Features of Clinical Stage I Lung Adenocarcinoma

Advanced lung cancers with epidermal growth factor receptor (EGFR) exon 19 deletions (Ex19s) and EGFR exon 21 L858R point mutations (Ex21s) exhibit different clinical behavior. However, these differences are unclear in resectable primary lung tumors.The clinicopathological features of 88 (20.9%) Ex19, 124 (29.4%) Ex21, and 198 (46.9%) EGFR wild-type (Wt) clinical stage I primary adenocarcinomas resected between January 1, 2012 and October 31, 2014 were compared by using Chi-square tests, residual error analysis, analysis of variance, and Tukey tests.Ex21 lesions occurred more frequently in women and never-smokers and had a higher tumor disappearance rate (TDR: 59.6% vs 43.9%; P < 0.001) and lower maximum standardized uptake value (maxSUV: 2.0 vs 3.5; P < 0.01) than Wt lesions; Ex19 lesions had intermediate values (52.8% and 2.6). There was a low frequency of vascular invasion in Ex21 lesions (12.1%; P < 0.05) and a high frequency in Wt lesions (22.7%; P < 0.05). Most Ex19 lesions were intermediate-grade adenocarcinoma (lepidic, acinar, and papillary predominant: 73.9%; P < 0.05). Wt and Ex21 lesions were predominately high-grade (micropapillary or solid predominant, mucinous variant) and low-grade (adenocarcinoma in situ and minimally invasive adenocarcinoma) adenocarcinoma, respectively. Wt lesions had smaller lepidic components (42.1% vs 56.3%; P < 0.001) and larger papillary and solid components (papillary: 15.5% vs 9.0%; P < 0.05; solid: 13.2% vs 3.2%; P < 0.001) than Ex21 lesions. Most Ex19 lesions had intermediate component rates.Most Ex21 lesions were low-grade adenocarcinoma with lepidic growth patterns. Wt high-grade adenocarcinomas included solid and papillary components with vascular invasion. Ex19 lesions were intermediate grade between Ex21 and Wt.