Durable Response to Tyrosine Kinase Inhibitor Therapy in a Lung Cancer Patient Harboring Epidermal Growth Factor Receptor Tandem Kinase Domain Duplication

EGFR kinase domain duplication in lung adenocarcinoma with systemic and intracranial response to a double-dose of furmonertinib: a case report and literature review

Background

EGFR kinase domain duplication (EGFR-KDD) is an infrequent oncogenic driver mutation in lung adenocarcinoma. It may be a potential target benefit from EGFR-tyrosine kinase inhibitors (TKIs) treatment.

Case presentation

A 66-year-old Chinese male was diagnosed with lung adenocarcinoma in stage IVb with brain metastases. Next-generation sequencing revealed EGFR-KDD mutation. The patient received furmonertinib 160mg daily for anti-cancer treatment and obtained therapeutic efficacy with partial response (PR). Progression-free survival (PFS) duration from monotherapy was 16 months. With slow progressions, combined radiotherapy and anti-vascular targeted therapy also brought a continuous decrease in the tumors. The patient has an overall survival (OS) duration of more than 22 months and still benefits from double-dose furmonertinib.

Conclusions

This report provided direct evidence for the treatment of EGFR-KDD to use furmonertinib. A Large-scale study is needed to confirm this preliminary finding.

Colorectal cancer harboring EGFR kinase domain duplication response to EGFR tyrosine kinase inhibitors

Epidermal growth factor receptor kinase domain duplication (EGFR-KDD) is a rare, recurrent oncogenic variant that constitutively activates EGFR in non-small-cell lung cancer. Herein, we report the case of a 70-year-old man with resectable colorectal adenocarcinoma who underwent surgery followed by adjuvant therapy. He relapsed with multiple liver metastases and received standard chemotherapy until his disease became refractory. Comprehensive genomic profiling of his postoperative colorectal cancer tissue revealed EGFR-KDD. He was treated with an EGFR tyrosine kinase inhibitor (TKI), afatinib and achieved a partial response (- 55%) after 8 weeks; however, he developed massive malignant ascites after 13 weeks. Osimertinib, another EGFR-TKI, controlled his tumors for 9 months. Patient-derived cancer organoids from his malignant ascites confirmed sensitivity to EGFR-TKIs. The findings suggest that EGFR-TKIs can be a potential treatment option for this molecular subgroup.

Expanding the Clinical Utility of Targeted RNA Sequencing Panels beyond Gene Fusions to Complex, Intragenic Structural Rearrangements

Gene fusions are a form of structural rearrangement well established as driver events in pediatric and adult cancers. The identification of such events holds clinical significance in the refinement, prognostication, and provision of treatment in cancer. Structural rearrangements also extend beyond fusions to include intragenic rearrangements, such as internal tandem duplications (ITDs) or exon-level deletions. These intragenic events have been increasingly implicated as cancer-promoting events. However, the detection of intragenic rearrangements may be challenging to resolve bioinformatically with short-read sequencing technologies and therefore may not be routinely assessed in panel-based testing. Within an academic clinical laboratory, over three years, a total of 608 disease-involved samples (522 hematologic malignancy, 86 solid tumors) underwent clinical testing using Anchored Multiplex PCR (AMP)-based RNA sequencing. Hematologic malignancies were evaluated using a custom Pan-Heme 154 gene panel, while solid tumors were assessed using a custom Pan-Solid 115 gene panel. Gene fusions, ITDs, and intragenic deletions were assessed for diagnostic, prognostic, or therapeutic significance. When considering gene fusions alone, we report an overall diagnostic yield of 36% (37% hematologic malignancy, 41% solid tumors). When including intragenic structural rearrangements, the overall diagnostic yield increased to 48% (48% hematologic malignancy, 45% solid tumor). We demonstrate the clinical utility of reporting structural rearrangements, including gene fusions and intragenic structural rearrangements, using an AMP-based RNA sequencing panel.

Structure-Guided Strategies of Targeted Therapies for Patients with EGFR-Mutant Non-Small Cell Lung Cancer

Oncogenic mutations within the EGFR kinase domain are well-established driver mutations in non-small cell lung cancer (NSCLC). Small-molecule tyrosine kinase inhibitors (TKIs) specifically targeting these mutations have improved treatment outcomes for patients with this subtype of NSCLC. The selectivity of these targeted agents is based on the location of the mutations within the exons of the EGFR gene, and grouping mutations based on structural similarities has proved a useful tool for conceptualizing the heterogeneity of TKI response. Structure-based analysis of EGFR mutations has influenced TKI development, and improved structural understanding will inform continued therapeutic development and further improve patient outcomes. In this review, we summarize recent progress on targeted therapy strategies for patients with EGFR-mutant NSCLC based on structure and function analysis.

Organoid drug screening report for a non-small cell lung cancer patient with EGFR gene mutation negativity: A case report and review of the literature

Patients with non-small cell lung cancer (NSCLC) who carry epidermal growth factor receptor (EGFR) mutations can benefit significantly from EGFR tyrosine kinase inhibitors (EGFR TKIs). However, it is unclear whether patients without EGFR mutations cannot benefit from these drugs. Patient-derived tumor organoids (PDOs) are reliable in vitro tumor models that can be used in drug screening. In this paper, we report an Asian female NSCLC patient without EGFR mutation. Her tumor biopsy specimen was used to establish PDOs. The treatment effect was significantly improved by anti-tumor therapy guided by organoid drug screening.

Tyrosine kinase altered spindle cell neoplasms with EGFR internal tandem duplications

In this study, we present two extra-renal pediatric spindle cell neoplasms with EGFR internal tandem duplications (ITD). Histologically, these tumors demonstrated the same histologic features seen in other tyrosine kinase altered spindle cell neoplasms, with one case showing abundant adipose tissue with cellular fibrous septae resembling lipofibromatosis and the other case showing fascicles of spindled cells resembling infantile fibrosarcoma. There was variable expression of CD34, S100 and SMA, and all cases were negative for panTRK. This case series adds to our molecular understanding of the spectrum of tyrosine kinase altered spindle cell neoplasms and represents the first reported examples of EGFR ITDs in extra-renal tumors. The presence of EGFR alterations in the absence of gene fusions represents a potential therapeutic target and necessitates a broader testing panel for this group of tumors. This article is protected by copyright. All rights reserved.

EGFR signaling pathway as therapeutic target in human cancers

Epidermal Growth Factor Receptor (EGFR) enacts major roles in the maintenance of epithelial tissues. However, when EGFR signaling is altered, it becomes the grand orchestrator of epithelial transformation, and hence one of the most world-wide studied tyrosine kinase receptors involved in neoplasia, in several tissues. In the last decades, EGFR-targeted therapies shaped the new era of precision-oncology. Despite major advances, the dream of converting solid tumors into a chronic disease is still unfulfilled, and long-term remission eludes us. Studies investigating the function of this protein in solid malignancies have revealed numerous ways how tumor cells dysregulate EGFR function. Starting from preclinical models (cell lines, organoids, murine models) and validating in clinical specimens, EGFR-related oncogenic pathways, mechanisms of resistance, and novel avenues to inhibit tumor growth and metastatic spread enriching the therapeutic portfolios, were identified. Focusing on non-small cell lung cancer (NSCLC), where EGFR mutations are major players in the adenocarcinoma subtype, we will go over the most relevant discoveries that led us to understand EGFR and beyond, and highlight how they revolutionized cancer treatment by expanding the therapeutic arsenal at our disposal.

Role of the EGFR-KDD mutation as a possible mechanism of acquired resistance of non-small cell lung cancer to EGFR tyrosine kinase inhibitors: A case report

Epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) are currently considered as the standard therapy for patients with advanced non-small cell lung cancer (NSCLC) who have EGFR-activating mutations. However, despite an initially profound response to these drugs, these patients ultimately develop drug resistance. The most common resistance mechanism is the development of a secondary mutation in EGFR (T790M), although activation of the MNNG/HOS transforming gene (MET), amplification of the Erb-B2 receptor tyrosine kinase 2 gene and histological transformation to small cell lung cancer may also lead to resistance. In addition, there may be additional, rare mechanisms leading to resistance that remain unidentified. Mutations in the EGFR kinase domain duplication (EGFR-KDD) are rare, although they act as oncogenic drivers in NSCLC. To the best of our knowledge, all studies to date have reported EGFR-KDD as the primary mutation in NSCLC. The aim of the present study was to report the case of an EGFR-KDD mutation in a patient with NSCLC who developed acquired resistance to gefitinib, but responded well to afatinib. Therefore, EGFR-KDD mutation is an additional potential mechanism underlying the development of acquired resistance to EGFR-TKIs.

Osimertinib is an effective epidermal growth factor receptor-tyrosine kinase inhibitor choice for lung cancer with epidermal growth factor receptor exon 18-25 kinase domain duplication: report of two cases

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) are an effective treatment for common EGFR mutations in non-small-cell lung cancer (NSCLC). Rarer EGFR mutations such as kinase domain duplications (KDDs) have been identified, but the optimal therapy following treatment resistance remains unknown. We report two patients who were diagnosed with NSCLC including KDD. For case 1, afatinib (40 mg once daily) was at first effective but then became ineffective. Consequently, osimertinib therapy (80 mg once daily) was administered. As of 26 May 2021, the osimertinib therapy achieved a stable disease state according to the chest computed tomography scan. As for case 2, the patient received second-line chemotherapy and anlotinib (12 mg once daily) for 6 months and died in May 2020. Here, we describe osimertinib as an effective therapy for EGFR-KDD positive lung adenocarcinoma and thereby provide a new alternative for further treatment following resistance to first- and second-generation EGFR-TKIs.

Acquired Resistance Mechanism of EGFR Kinase Domain Duplication to EGFR TKIs in Non-Small Cell Lung Cancer

PURPOSE

Epidermal growth factor receptor kinase domain duplication (EGFR-KDD) is a rare and poorly understood oncogenic mutation in non-small cell lung cancer (NSCLC). We aimed to investigate the acquired resistance mechanism of EGFR-KDD against EGFR-TKIs.

MATERIALS AND METHODS

We identified EGFR-KDD in tumor tissue obtained from a patient with stage IV lung adenocarcinoma and established the patient-derived cell line SNU-4784. We also established several EGFR-KDD Ba/F3 cell lines: EGFR-KDD wild type (EGFR-KDDWT), EGFR-KDD domain 1 T790M (EGFR-KDDD1T), EGFR-KDD domain 2 T790M (EGFR-KDDD2T), and EGFR-KDD both domain T790M (EGFR-KDDBDT). We treated the cells with EGFR tyrosine kinase inhibitors (TKIs) and performed cell viability assays, immunoblot assays, and ENU (N-ethyl-N-nitrosourea) mutagenesis screening.

RESULTS

In cell viability assays, SNU-4784 cells and EGFR-KDDWT Ba/F3 cells were sensitive to 2nd generation and 3rd generation EGFR TKIs. In contrast, the T790M-positive EGFR-KDD Ba/F3 cell lines (EGFR-KDDT790M) were only sensitive to 3rd generation EGFR TKIs. In ENU mutagenesis screening, we identified the C797S mutation in kinase domain 2 of EGFR-KDDBDT Ba/F3 cells. Based on this finding, we established an EGFR-KDD domain 1 T790M/domain 2 cis-T790M+C797S (EGFR-KDDT/T+C) Ba/F3 model, which was resistant to EGFR TKIs and anti-EGFR monoclonal antibody combined with EGFR TKIs.

CONCLUSION

Our study reveals that the T790M mutation in EGFR-KDD confers resistance to 1st and 2nd generation EGFR TKIs, but is sensitive to 3rd generation EGFR TKIs. In addition, we identified that the C797S mutation in kinase domain 2 of EGFR-KDDT790M mediates a resistance mechanism against 3rd generation EGFR TKIs.

Durable response to EGFR tyrosine kinase inhibitors in a patient with non-small cell lung cancer harboring an EGFR kinase domain duplication

Epidermal growth factor receptor (EGFR) kinase domain duplication (KDD) has been identified as an oncogenic driver in 0.05% to 0.14% of non-small cell lung cancer (NSCLC) patients. However, little is known of the efficacy of EGFR tyrosine kinase inhibitors (TKIs) for such patients. Here, we report the case of a 45-year-old Japanese woman with NSCLC positive for EGFR-KDD (duplication of exons 18-25) who developed carcinomatous meningitis and showed a marked response to the EGFR-TKIs erlotinib and osimertinib. As far as we are aware, this is the first report of EGFR-TKI efficacy for carcinomatous meningitis in a NSCLC patient harboring EGFR-KDD.

Lung Adenocarcinoma Patient Harboring EGFR-KDD Achieve Durable Response to Afatinib: A Case Report and Literature Review

The rapid development of epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors (TKIs) has revolutionized the treatment of patients with advanced or metastatic non-small cell lung cancer (NSCLC) harboring EGFR mutations including but not limited to exon 19 deletions (19 del) and point mutation L858R in exon 21. However, the efficacy of EGFR-TKIs in patients with rare mutations, such as EGFR-kinase domain duplication (KDD), remains elusive. EGFR-KDD often results from in-frame tandem duplication of EGFR exons 18-25, causing subsequent constitutive activation of EGFR signaling. Several case reports have revealed the efficacies of EGFR-TKIs in advanced lung adenocarcinoma (LUAD) with EGFR-KDD but yielded variable antitumor responses. In the present study, we report a 61-year-old male patient diagnosed with T1N3M0 (stage IIIB) LUAD harboring EGFR-KDD involving exons 18-25. He was treated with afatinib and achieved partial response (PR) with progression-free survival (PFS) of 12 months and counting. Our work, confirming EGFR-KDD as an oncogenic driver and therapeutic target, provides clinical evidence to administer EGFR-TKIs in patients with advanced LUAD harboring EGFR-KDD.

Lung Adenocarcinoma Harboring EGFR Kinase Domain Duplication (EGFR-KDD) Confers Sensitivity to Osimertinib and Nivolumab: A Case Report

Background

Kinase domain duplication of EGFR (EGFR-KDD) is a rare oncogenic driver alteration and serves as a potential therapeutic target. Its effect on EGFR-tyrosine kinase inhibitors (TKIs), especially the third-generation drug Osimertinib, and immune checkpoint inhibitors (ICIs) remains inconclusive.

Case Presentation

A 45-year old male with lung adenocarcinoma progressed with liver metastasis after receiving pemetrexed and cisplatin as adjuvant chemotherapy. Targeted next-generation sequencing (NGS) identified an EGFR-KDD in the resected left upper lung. Icotinib was used in the following treatment and the liver metastasis was found to shrink but the progression-free survival (PFS) only lasted for 4 months with the appearance of right hepatic metastasis. Meantime, the same EGFR-KDD was identified in the left hepatic re-biopsy. Afterward, the patient benefited from the third-line therapy of Osimertinib with a PFS as long as 21 months. Then he progressed with enlarged mediastinal lymph nodes, and targeted NGS consistently identified EGFR-KDD, as well as a new RELN p.G1774E mutation. Given the continually increasing tumor mutation burden (TMB, 3.4 mutation/Mb) and PD-L1 expression-based tumor proportion score (TPS, 1%), Nivolumab was used as the fourth-line salvage therapy, which lead to considerable efficacy, with decreased blood carcinoembryonic antigen (CEA), regressed mediastinal lymph nodes, and reduced liver metastases.

Conclusions

Our case provided direct evidence to support the role of Osimertinib in the treatment of EGFR-KDD, as well as added valuable insights into application of immune-based therapeutics in the specific subgroups bearing EGFR alteration(s).

The landscape of kinase domain duplication in Chinese lung cancer patients

Background

Kinase domain duplication (KDD) is a special type of large genomic rearrangement (LGR), occurring in the kinase domain of protein kinase genes. KDD of some lung cancer driver genes, such as

EGFR

KDD, has been identified and implicated to be oncogenic in non-small cell lung cancer (NSCLC). The present study aims to interrogate the spectrum of KDD occurring on classic driver genes in Chinese lung cancer patients without the presence of classic lung cancer driver mutations.

Methods

We retrospectively enrolled 10,525 Chinese lung cancer patients who met the following inclusion criteria; (I) do not carry classic lung cancer driver mutations in any of the 8 driver genes and (II) tyrosine kinase inhibitor (TKI)-naïve. Capture-based targeted sequencing was performed on tissue or plasma samples. LGR and KDD were identified by using in-house analysis scripts. The prevalence and distribution of LGR and KDD in our cohort were analyzed.

Results

The median age of the cohort was 64 years with 68.7% being male. Among all patients, 23.2% and 51.8% were diagnosed with stage III and IV disease respectively. We identified 43 cases (0.41%) harboring LGR in one of the driver genes (EGFR/ERBB2/ALK/RET/ROS1/MET/BRAF), with 24 (0.23%) patients harboring KDD. Of the patients harboring KDD, a majority (n=19) harbored canonical EGFR-KDD involving exons 18–25, whilst one patient harbored duplications of EGFR exons 18–26. There were three MET-KDD patients; in two, the alteration occurred in exons 15–21 and in one, the alteration occurred in exons 3–21. One patient harbored RET-KDD involving exons 12–18. KDD showed a comparable prevalence in lung adenocarcinoma (LUAD) and lung squamous cell carcinoma (LUSC) (0.33% vs. 0.11%, P=0.118). Nineteen non-KDD LGRs, spanning six genes including EGFR (n=6), MET (n=3), ALK (n=4), ROS1 (n=2), ERBB2 (n=2) and BRAF (n=2), were found, each occurring in one patient. The prevalence of LGR in LUADs and LUSCs was comparable (0.55% vs. 0.38%, P=0.452).

Conclusions

We observed a prevalence of 0.41% and 0.23% for LGR and KDD, respectively. Twenty-four different LGR alterations, including 5 KDDs and 19 non-KDD LGRs, were observed. KDDs mainly occurred in EGFR involving exons 18–25 and non-KDD LGRs were distributed more randomly. The prevalence of LGR/KDD in LUSCs and LUADs was comparable.

Congenital mesoblastic nephroma is characterised by kinase mutations including EGFR internal tandem duplications, the ETV6-NTRK3 fusion, and the rare KLHL7-BRAF fusion

AIMS

Congenital mesoblastic nephroma (CMN) is histologically classified into classic, cellular and mixed subtypes. The aims of this study were to characterise the clinical, pathological and molecular features of a series of CMNs, and to determine the utility of pan-Trk and epidermal growth factor receptor (EGFR) immunohistochemistry as surrogate markers for NTRK gene fusions and EGFR internal tandem duplications (ITDs).

METHODS AND RESULTS

Twenty-two archival CMN cases (12 classic, five cellular, and five mixed) were tested for the ETV6-NTRK3 fusion and EGFR ITD transcripts by the use of reverse transcriptase polymerase chain reaction (PCR), and next-generation sequencing-based anchored multiplex PCR. All 12 classic CMNs had EGFR ITD. Of the five cellular CMNs, four had the ETV6-NTRK3 fusion and one had the KLHL7-BRAF fusion. Of the five mixed CMNs, four had EGFR ITD, and one had the ETV6-NTRK3 fusion. Pan-Trk immunoreactivity was 100% sensitive and 94.1% specific for the presence of NTRK rearrangement. However, EGFR staining was only 62.5% sensitive and 33.3% specific for EGFR ITD.

CONCLUSIONS

EGFR ITD is a consistent genetic event in classic CMN. A majority of cellular CMNs have the ETV6-NTRK3 fusion. Rare cellular CMNs may harbour non-canonical mutations such as the KLHL7-BRAF fusion, which was found in one case. Mixed CMNs may have either EGFR ITD or the ETV6-NTRK3 fusion. Pan-Trk immunohistochemistry is a sensitive, albeit not perfectly specific, marker for NTRK rearrangement. EGFR immunohistochemistry is not helpful as a marker of EGFR ITD.

A Novel Oncogenic Driver in a Lung Adenocarcinoma Patient Harboring an EGFR-KDD and Response to Afatinib

Introduction: Oncogenic mutations in the epidermal growth factor receptor (EGFR) occur frequently in patients with lung cancer. These mutations may serve as critical predictive biomarkers in patients with non-small cell lung cancer (NSCLC). Among them, EGFR exon 18–25 kinase domain duplication (EGFR-KDD) mutations have been identified as a novel EGFR gene subtype in NSCLC.

Case Presentation: We reported a rare case of a 59-year-old male diagnosed with adenocarcinoma. A biopsy revealed an EGFR-KDD identified by the next generation sequencing (NGS). Effective treatment outcome has been observed after administration with afatinib.

Conclusion: This case highlights that comprehensive NGS technique is valuable in detecting novel genetic mutations in tumors.

Recurrent EGFR alterations in NTRK3 fusion negative congenital mesoblastic nephroma

Objectives

To identify oncogenic driver mutations in congenital mesoblastic nephroma (CMN) cases lacking ETV6-NTRK3 fusion and discuss their diagnostic value.

Design

The institutional pathology database was queried for cases with a morphologic diagnosis of CMN. Cases positive for ETV6 rearrangement or with unavailable blocks were excluded. Four cases met the inclusion criteria and were sequenced by next-generation sequencing. Three additional cases were contributed by our collaborators.

Results

Three of four internal cases harbor an EGFR kinase domain duplication (KDD), which is known to be oncogenic yet exceedingly rare in other histologies. All three outside cases are positive for EGFR alterations, including KDD in two and a splicing site mutation in one. The splicing site mutation is predicted to be EGFR activating. One of the outside cases was a retroperitoneal mass without a clear site of origin. A diagnosis of CMN is suggested based on exclusion of differential diagnoses by expert consultation and detection of EGFR KDD.

Conclusions

EGFR activation, predominantly via EGFR KDD, is a common recurrent genetic alteration in CMN lacking NTRK3 fusions. CMN can be molecularly classified into NTRK3 fusion type, EGFR activation type and others.

Rare epidermal growth factor receptor (EGFR) mutations in non-small cell lung cancer

Epidermal growth factor receptor (EGFR) mutations are the second most common oncogenic driver event in non-small cell lung cancer (NSCLC). Classical activating mutations (exon 19 deletions and the L858R point mutation) comprise the vast majority of EGFR mutations and are well defined as strong predictors for good clinical response to EGFR tyrosine kinase inhibitors (EGFRi). However, low frequency mutations including point mutations, deletions, insertions and duplications occur within exons 18-25 of the EGFR gene in NSCLC and are associated with poorer responses to EGFRi. Despite an increased uptake of more sensitive detection methods to identify rare EGFR mutations in patients, our understanding of the biology of these rare EGFR mutations is poor compared to classical mutations. In particular, clinical data focused on these mutations is lacking due to their rarity and challenges in trial recruitment, resulting in an absence of effective treatment strategies for many low frequency EGFR mutations. In this review, we describe the structural and mechanistic features of rare EGFR mutations in NSCLC and discuss the preclinical and clinical evidence for EGFRi response for individual rare EGFR mutations. We also discuss EGFRi sensitivity for complex EGFR mutations, and conclude by offering a perspective on the outstanding questions and future steps required to make advances in the treatment of NSCLC patients that harbour rare EGFR mutations.

Chemotherapy combined with bevacizumab for the treatment of advanced lung adenocarcinoma cancer harboring EGFR-ANXA2, EGFR-RAD51, ATR and BRCA2 mutations: A case report

Here, we report a case of a 36‐year‐old female patient with metastatic non‐small cell lung cancer (NSCLC) harboring EGFR‐ANXA2 and EGFR‐RAD51 double fusion mutations with BRCA2 (nonsense mutation of exon 11) and ATR mutations (Exon 44 variable shear mutation) identified by next generation sequencing (NGS). The efficacy was significantly improved after lobaplatin combined with pemetrexed, temozolomide and bevacizumab. This is the first report of a novel mutation type EGFR‐ANXA2, as well as double EGFR fusion mutations in advanced lung adenocarcinoma. Furthermore, platinum‐based chemotherapy plus bevacizumab rather than targeted therapy showed favorable effects in this patient, providing a novel therapeutic conception for patients, even with multidriver mutations.

Clinical outcomes of EGFR kinase domain duplication to targeted therapies in NSCLC

Kinase domain duplications of the epidermal growth factor receptor (EGFR‐KDD) have been identified and implicated to be oncogenic in nonsmall cell lung cancers (NSCLCs). However, its prevalence and clinical contributions in lung cancer are largely unknown. Here, we conducted a multicenter record review of 10,759 NSCLC patients who underwent genetic testing using next‐generation sequencing (NGS) targeting EGFR exons and the introns involved in EGFR‐KDD rearrangements. EGFR‐KDDs were identified in a total of 13 patients, which is approximately 0.12% of the total population reviewed, and also consisted of 0.24% (13/5394) of EGFR mutation‐positive patients. A total of 85% of patients (11/13) were identified with the canonical EGFR‐KDD duplication of exons 18–25, while the remaining two cases harbored duplications of EGFR exons 14–26 and exons 17–25, which have not been previously described. Importantly, none of the 13 patients had other coexisting driver mutations, highlighting the potential oncogenic role of this type of alteration. Three out of five patients who had exon 18–25 duplications showed partial antitumor responses to targeted therapies, while the other two patients demonstrated no clinical improvement. Furthermore, our data suggested that the EGFR T790 M mutation and EGFR amplification may represent the major resistance mechanisms against targeted therapies in tumors bearing EGFR‐KDD. In summary, our findings provide valuable insight into the prevalence of EGFR‐KDDs in NSCLCs and their clinical outcomes to targeted therapies.

What's new?

A rare class of mutation could provide a therapeutic target for lung cancer. Many NSCLCs arise with mutations in the EGFR tyrosine kinase domain, and treatment with EGFR tyrosine kinase inhibitors often boosts survival in these patients. Usually, these are deletions or point mutations, but sometimes the mutation is a kinase domain duplication (KDD). These authors investigated how frequently EGFR‐KDDs occur, and whether tyrosine kinase inhibitors work against them. By reviewing records from thousands of NSCLC patients, they discovered 13 EGFR‐KDDs. Tyrosine kinase inhibitors did suppress some of the tumors, although resistance arose in the event of additional EGFR mutations.

RET rearrangements are actionable alterations in breast cancer

Fusions involving the oncogenic gene RET have been observed in thyroid and lung cancers. Here we report RET gene alterations, including amplification, missense mutations, known fusions, novel fusions, and rearrangements in breast cancer. Their frequency, oncogenic potential, and actionability in breast cancer are described. Two out of eight RET fusions (NCOA4-RET and a novel RASGEF1A-RET fusion) and RET amplification were functionally characterized and shown to activate RET kinase and drive signaling through MAPK and PI3K pathways. These fusions and RET amplification can induce transformation of non-tumorigenic cells, support xenograft tumor formation, and render sensitivity to RET inhibition. An index case of metastatic breast cancer progressing on HER2-targeted therapy was found to have the NCOA4-RET fusion. Subsequent treatment with the RET inhibitor cabozantinib led to a rapid clinical and radiographic response. RET alterations, identified by genomic profiling, are promising therapeutic targets and are present in a subset of breast cancers.

Fusions of the gene RET have been described in thyroid and lung cancers. Here, the AUs identify RET gene alterations, including known fusions, novel fusions, and rearrangements in breast cancer (BC) that are involved in the tumorigenic process and show the benefit of RET therapy in a recurrent BC patient carrying the NCOA4-RET fusion.

Kinase inhibitor-responsive genotypes in EGFR mutated lung adenocarcinomas: moving past common point mutations or indels into uncommon kinase domain duplications and rearrangements

The most frequent epidermal growth factor receptor (EGFR) mutations found by traditional or comprehensive molecular profiling of lung adenocarcinomas include indels of exon 19 (the exon 19 deletion delE746_A750 being the most common) and the exon 21 L858R point mutation. The current approval labels for first line palliative gefitinib 250 mg/day, erlotinib 150 mg/day and afatinib 40 mg/day for advanced lung cancers require the presence of the aforementioned classical/sensitizing EGFR mutations. Other gefitinib, erlotinib and afatinib sensitizing mutations include exon 18 indels, G719X, exon 19 insertions, A763_Y764insFQEA, S768I and L861Q; for which off-label EGFR kinase inhibitor use is generally agreed upon by thoracic oncologists. The main biological mechanism of resistance to approved first line EGFR inhibitors is the selection/acquisition of EGFR-T790M that in itself can be inhibited by osimertinib 80 mg/day, a 3(rd) generation EGFR inhibitor that is bypassed by EGFR-C797X mutations. Another class of de novo inhibitor insensitive mutation includes EGFR exon 20 insertions. More recently, the dichotomy of only point mutations or indels explaining aberrant kinase activation of EGFR plus inhibitor response has been shattered by the discovery of uncommon (<0.5% of all EGFR mutations) genomic events involving exon 18-25 kinase domain duplications (KDD) and rearrangements (EGFR-RAD51 or EGFR-PURB). The latter lead to oncogene addiction, enhanced sensitivity to kinase inhibitors in vitro and clinical responses to approved EGFR inhibitors. The enhanced landscape of EGFR inhibitor-responsive genotypes highlights that comprehensive molecular profiling may be necessary to maximize the identification of all cases that can benefit from precision oncology.

EGFR Fusions as Novel Therapeutic Targets in Lung Cancer

Here, we report that novel epidermal growth factor receptor (EGFR) gene fusions comprising the N-terminal of EGFR linked to various fusion partners, most commonly RAD51, are recurrent in lung cancer. We describe five patients with metastatic lung cancer whose tumors harbored EGFR fusions, four of whom were treated with EGFR tyrosine kinase inhibitors (TKI) with documented antitumor responses. In vitro, EGFR-RAD51 fusions are oncogenic and can be therapeutically targeted with available EGFR TKIs and therapeutic antibodies. These results support the dependence of EGFR-rearranged tumors on EGFR-mediated signaling and suggest several therapeutic strategies for patients whose tumors harbor this novel alteration.

SIGNIFICANCE

We report for the first time the identification and therapeutic targeting of EGFR C-terminal fusions in patients with lung cancer and document responses to the EGFR inhibitor erlotinib in 4 patients whose tumors harbored EGFR fusions. Findings from these studies will be immediately translatable to the clinic, as there are already several approved EGFR inhibitors. Cancer Discov; 6(6); 601-11. ©2016 AACR.See related commentary by Paik, p. 574This article is highlighted in the In This Issue feature, p. 561.