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CASE REPORT
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Epidermal growth factor receptor-activating mutation(E746_T751>VP) in pancreatic ductal adenocarcinoma responds to erlotinib, followed by epidermal growth factor receptor resistance-mediating mutation (A647T): A case report and literature review


1 Department of Oncologic Sciences, Mitchell Cancer Institute, The University of South Alabama, Mobile, Alabama, USA
2 College of Allied Health Professions, The University of South Alabama, Mobile, Alabama, USA
3 Division of Interventional Radiology, The University of South Alabama, Mobile, Alabama, USA
4 Medical Oncology, Mitchell Cancer Institute, The University of South Alabama, Mobile, Alabama, USA
5 Gynecology Oncology, Mitchell Cancer Institute, The University of South Alabama, Mobile, Alabama, USA
6 Medical Oncology, The James Comprehensive Cancer Center, The Ohio State University, Columbus, OH, USA

Date of Submission01-Nov-2018
Date of Decision15-Feb-2019
Date of Acceptance15-May-2019
Date of Web Publication30-Jan-2020

Correspondence Address:
Moh'd Khushman,
Department of Medical Oncology, The University of South Alabama, Mitchell Cancer Institute, 1660 Spring Hill Ave, Mobile, AL 36694
USA
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jcrt.JCRT_729_18

 > Abstract 


Despite recent advances in treatment with multidrug chemotherapy regimens, outcomes of patients with advanced pancreatic ductal adenocarcinoma (PDAC) remain very poor. Treatment with targeted therapies has shown marginal benefits due to intrinsic or acquired resistance. Actionable mutations, while detected infrequently in patients with PDAC, are becoming increasingly used in personalized medicine. Here, we describe an epidermal growth factor receptor (EGFR)-activating mutation (E746_T751>VP) to erlotinib, a first-generation tyrosine kinase inhibitor (TKI), in a patient with metastatic PDAC. After an initial partial response to erlotinib for 12 months, the patient's disease progressed with emergence of the EGFR A647T mutation. Certainly, the patient also progressed after switching therapy to a third-generation EGFR TKI (osimertinib). This case illustrates the posttreatment evolution of EGFR A647T-mediated resistance to the first- and third-generation TKIs. To our knowledge, this is the first case to report the aforementioned activating and resistance-mediated mutations. In summary, genomic analysis performed in this patient with PDAC on the tumor biopsy and peripheral blood provided tools to understand mechanisms of response and resistance to targeted therapy with EFGR TKIs.

Keywords: A647T, E746_T751>VP mutation, epidermal growth factor receptor, erlotinib, osimertinib, pancreatic ductal adenocarcinoma, resistance



How to cite this URL:
Patel GK, Perry JB, Abdul-Rahim O, Frankel AE, Cameron D, Taylor W, Rocconi RP, Abushahin L, Nelson C, Singh AP, Khushman M. Epidermal growth factor receptor-activating mutation(E746_T751>VP) in pancreatic ductal adenocarcinoma responds to erlotinib, followed by epidermal growth factor receptor resistance-mediating mutation (A647T): A case report and literature review. J Can Res Ther [Epub ahead of print] [cited 2020 Feb 29]. Available from: http://www.cancerjournal.net/preprintarticle.asp?id=277359

Girijesh Kumar Patel and Josiah B Perry, contributed equally to this work





 > Introduction Top


Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest malignancies. Around 92% of patients succumb to PDAC within 5 years of diagnosis. It is the fourth leading cause of cancer-related death in the United States and second only to colorectal cancer as a cause of digestive cancer-related death.[1] Despite recent advancements in therapeutic regimens with leucovorin, fluorouracil, irinotecan plus oxaliplatin (FOLFIRINOX), Nab-paclitaxel plus gemcitabine, and fluorouracil plus nanoliposomal irinotecan, outcomes continue to be disappointing.[2],[3],[4] Treatment with targeted therapies has shown marginal benefits due to intrinsic or acquired resistance.[5] Nonetheless, personalized medicine using the patient's own genetic signature has been reported to help with selecting targeted therapy after identification of actionable molecular targets.[6]

This case report describes a patient with PDAC that harbored the epidermal growth factor receptor (EGFR) E746_T751>VP mutation. Treating this patient with erlotinib, a first-generation tyrosine kinase inhibitor (TKI), resulted in a partial and durable response that lasted for 12 months. Disease progression after treatment with erlotinib was associated with emergence of EGFR A647T mutation. Treatment with osimeritinib, third-generation EGFR TKI, was considered later on by the treating oncologist (off-label use). Certainly, the patient experienced disease progression 3 months later, and shortly thereafter she passed away. This case illustrates posttreatment evolution of EGFR A647T-mediated resistance to the first- and third-generation EGFR TKIs. To our knowledge, this is the first case to report the aforementioned activating and resistance-mediated mutations, making this case novel.


 > Case Report Top


A 76-year-old Caucasian female patient was diagnosed with stage IV PDAC with pelvic metastatic lesion in 2014. The pelvic lesion was biopsied and pathology showed adenocarcinoma that is similar in morphology to the adenocarcinoma seen on the pancreas fine-needle aspirate. Moreover, the neoplastic cells were positive for CK7 and CDX2 and negative for CK20. At the time of diagnosis, the tumor biopsy was sent to Foundation Medicine (Cambridge, MA) for next-generation sequencing (NGS). The tumor was found to harbor genomic alterations that have therapeutic implications. NGS identified the EGFR E746_T751>VP mutation, a deletion in exon 19 with insertion of VP amino acids encoding a stretch of the kinase domain of EFGR. NGS also identified other genomic alterations (BRIP1 F600L, CDKN2A p16INK4a R800* and p14ARF P94L, DNMT3A splice site 2174-2A>G, RNF43 R113*, and TGFBR2 R528H) [Supplementary Figure 1]. Notably, NGS revealed the wild-type KRAS gene.
Figure 1: Contrast-enhanced computed tomography scan done before and after the erlotinib treatment. (a) Represents a contrast-enhanced computed tomography scan (done prior to treatment with erlotinib) showing a 3.2 cm × 2.2 cm pelvic mass between the uterus and rectum. (b) Represents contrast-enhanced computed tomography scan (done 3 months after starting erlotinib) showing partial/almost complete response of the pelvic mass. The disease in the pancreas was stable (not shown here)

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The patient was treated with systemic palliative chemotherapy with FOLFIRINOX. Treatment was poorly tolerated due to diarrhea and thrombocytopenia despite regimen modifications and dosage adjustments. Six months after starting FOLFIRINOX, her disease progressed and she was switched to erlotinib. Erlotinib monotherapy at 75 mg daily was well tolerated and resulted in a stable disease in the pancreas but partial/almost complete and durable response in the pelvic metastatic lesion that lasted for 12 months [Figure 1]. Then, her disease progressed so she was switched to gemcitabine plus Nab paclitaxel. Certainly, treatment was poorly tolerated due to bone marrow toxicity.



At that time, the patient's peripheral blood was sent for molecular analysis through Guardant Health, Inc., (Redwood City, CA, USA). Blood was collected in Streck™ tubes during routine phlebotomy, and samples were shipped at room temperature overnight. About 10 mL of blood was processed upon receipt to isolate plasma by centrifugation at 1600 g for 10 min at 4°C. Plasma was immediately aliquoted and stored at −70°C. Cell-free DNA (cfDNA) was extracted from 1 mL aliquots of plasma using the QIAamp circulating nucleic acid kit (Qiagen), concentrated using Agencourt Ampure XP beads (Beckman Coulter), and quantified by Qubit fluorometer (Life Technologies, Carlsbad, CA, USA). All cfDNA sequencing and analyses were performed at Guardant Health (Redwood City, Calif, USA). The circulating cfDNA in the blood was found to harbor EGFR A647T mutation. The patient was treated with osimertinib at 80 mg daily in an off-label use since osimertinib is not approved by the Food and Drug Association (FDA) in patients with PDAC. The patient's disease progressed 3 months later [Figure 2], so osimertinib was discontinued. The patient's general condition and her performance status rapidly declined. She was thus deemed not a candidate for further therapy and was referred to hospice. Two months after stopping osimertinib, she expired.
Figure 2:Contrast-enhanced computed tomography scan of done before and after the osimertinib treatment. (a) Represents a contrast-enhanced computed tomography scan (done prior to treatment with osimertinib) showing a 4.4 cm × 4.1 cm pelvic mass between the uterus and rectum. (b) Represents contrast-enhanced computed tomography scan (done 3 months after starting osimertinib) showing interval disease progression of the pelvic mass. The degree of progression in the pancreas was less pronounced (not shown)

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 > Discussion Top


EGFR is a transmembrane glycoprotein expressed on the cell surface of both normal as well as cancer cells. EGFR regulates key processes in the cell including proliferation, survival, differentiation, and homeostasis. Ligand binding with EGFR leads to formation of homo- or heterodimers (with ERBB2, ERBB3, or ERBB4) and autophosphorylation, ultimately inducing intracellular signaling pathways under normal physiological conditions.[7] The general schematic diagram for the EGFR signaling and inhibition is represented in [Figure 3]. EGFR plays a crucial role in carcinogenesis when it is mutated or structurally altered.[8],[9] Overexpression of EGFR and ERBB2 has been reported hypoxic microenvironments and is positively correlated with aggressiveness and poor outcome in different human malignancies, including the lung, head and neck, breast, ovarian, bladder, colorectal, and PDAC.[10]
Figure 3:Mechanistic representation of epidermal growth factor receptor signaling and inhibition by anti-epidermal growth factor receptor antibody and small molecule inhibitors. There are 11 ligands (EGF, TGFα), HB EGF-like growth factor, amphiregulin, beta-cellulin, epiregulin, and epigen known to bind and activate epidermal growth factor receptor. Ligand binding to epidermal growth factor receptor on the cell surface induces receptor dimerization and cross-phosphorylation of the cytoplasmic tyrosine kinase domain, which triggers downstream signaling through effector and adaptor proteins. The principal pathways included are (1) RAS/RAF/MEK, (2) PI3K/AKT, and (3) JAK/STAT, pathways resulting in cell proliferation, invasion, migration, and inhibition of apoptosis. The anti-epidermal growth factor receptor antibody or small molecule inhibitors are used as targeted therapy where overexpression or actionable mutations are present in epidermal growth factor receptor gene, respectively. EGF = epidermal growth factor, EGFR = Epidermal growth factor receptor, JAK = Janus kinase, MAPK = Mitogen-activated protein kinase, MEK = MAPK/extracellular signal-regulated kinase kinase, mTOR = Mammalian target of rapamycin, PI3K = Phosphatidylinositol-3 kinase, STAT = Signal transducer and activator of transcription, TGFα = Transforming growth factor α, HB = Heparin binding

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EGFR-activating mutations in exons 19 through 21 are most common in nonsmall cell lung cancer (NSCLC). They are rare but have been reported in a wide spectrum of other malignancies, including the biliary tract, esophagus, colon, head and neck, prostate, kidney, and soft tissue sarcoma.[11],[12],[13] In PDAC, the EGFR pathway is overexpressed in around 90% of tumors.[14] However, like most other solid tumors, PDAC tumors rarely exhibit activating mutations in EGFR.[15],[16],[17],[18] The Cancer Genome Atlas database reports EGFR mutations in 1 of 149 tumors (0.7%), and the COSMIC database reports EGFR mutations in 6 of 1599 (0.37%).[16],[17]

In patients with advanced NSCLC with EGFR-activating mutations (exon 19 deletions and L858R point mutation in exon 21), treatment with EGFR TKIs ( first and second generation) significantly prolonged progression-free survival (PFS) compared to platinum-based chemotherapy.[19] In patients with PDAC, compared to gemcitabine monotherapy, a first-generation EGFR TKI (erlotinib) plus gemcitabine showed a statistically significant survival benefit (5.91 vs. 6.24 months).[15] This survival benefit (10 days) was considered by most medical oncologists not clinically meaningful. This randomized Phase III clinical trial was criticized because the treatment with erlotinib was given to an unselected population, especially given the low frequency of activating mutations in EGFR. Moreover, the KRAS mutation (frequently observed in patients with PDAC) is postulated to predict resistance to treatment with TKIs targeting EGFR. The predictive role of EGFR and KRAS mutations was subsequently explored in a prospective trial. Erlotinib plus gemcitabine was found to be more effective than gemcitabine alone, especially in those with EFGR mutations. This combination therapy showed a statistically significant improvement in disease control (85% vs. 33%; P = 0.001), median PFS (5.9 vs. 2.4 months; P = 0.004) and median OS (8.7 vs. 6.0 months; P = 0.044). The KRAS mutation was not associated with treatment response or survival.[20]

The NGS performed on our patient's metastatic tumor identified the EGFR E746_T751>VP mutation. The EGFR mutation identified is a deletion (E746_T751) and insertion (VP) in exon 19, encoding a portion of the kinase domain of EFGR shown in [Figure 4]. Deletions in exon 19 of EGFR are well described in patients with lung adenocarcinoma, in which they confer sensitivity to EGFR TKIs. Given the described genomic profile, the patient was treated with erlotinib. Clearly, the patient experienced a partial/almost complete and durable response in the pelvic mass that lasted for 12 months. The PFS experienced in our patient is longer than the median PFS of 5.9 months described in the prospective trial by Wang et al.[20]
Figure 4:A schematic diagram of epidermal growth factor receptor showing the distribution of exons in the extracellular domain (epidermal growth factor binding), transmembrane domain, and intracellular domain (comprising of the tyrosine kinase and autophosphorylation regions). Exons 18–21 in the tyrosine kinase region where the relevant mutations are located are expanded (represented by the purple bar), and a detailed list of epidermal growth factor receptor mutations in these exons that are associated with sensitivity (purple boxes at bottom) or resistance (red boxes in the middle) to gefitinib or erlotinib is shown. The sensitizing (epidermal growth factor receptor E746 T751>VP) and resistance-mediated (epidermal growth factor receptor A647) mutations described in our case are shown in this figure are highlighted in red boxes

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The causes of acquired resistance to EGFR TKIs in patients with NSCLC are not fully understood, but they include secondary mutations in EGFR and amplification of the MET signaling pathway.[21],[22] About 50% of acquired resistance to TKIs is due to the T790M mutation. In addition to the T790M mutation, three other secondary mutations in EGFR have been reported: T854A, L747S, and D761Y.[23],[24] The third-generation EGFR TKI (osimertinib) was initially approved in patients with acquired resistance to earlier generation EGFR TKIs through the T790M mutation.[25] In April 2018, in patients with NSCLC, osimertinib was approved by the FDA as a first-line therapy in patients with exon 19 deletions and the L858R point mutation in exon 21. The safety profile of osimertinib was similar to that of first-generation EFGR TKIs, but with somewhat lower rates of adverse events of Grade 3 or higher, despite a longer median duration of exposure with osimertinib.[26]

To date, little has been studied about the resistance mechanisms to EGFR TKIs in patients with PDAC. Further understanding of the mechanisms of resistance will facilitate the development of more effective ways to overcome acquired TKI resistance in PDAC. As in patients with NSCLC, the emergence of the T790M mutation in a patient with PDAC has been reported to confer resistance to erlotinib.[26] However, in the reported case, the patient did not respond to subsequent treatment with osimertinib.[27] The mechanism of acquired resistance to erlotinib in our patient is postulated to be through the emergence of the EGFR A647T mutation which is present in the cytoplasmic side of the transmembrane domain located in exon 17 [Figure 4].


 > Conclusions Top


This case describes an EGFR-activating mutation (E746_T751>VP) in a patient with metastatic PDAC that experienced a partial and durable response that lasted for 12 months to a first-generation TKIs (erlotinib). It also illustrates posttreatment evolution of EGFR mutation (A647T) mediating resistance to erlotinib and third-generation (osimertinib) TKIs. To our knowledge, this is the first and novel case to report the EFGR E746 T751>VP activating mutation to erlotinib and A647T-mediated resistance to erlotinib and osimertinib in a patient with PDAC. In summary, genomic analysis performed in this patient with PDAC on the tumor biopsy and peripheral blood provided tools to understand mechanisms of response and resistance to targeted therapy with EFGR TKIs in a patient with PDAC. This case also emphasizes the need to develop new generations TKIs that can treat patients harboring resistance-mediated mutations with, ideally, similar or better safety profile compared to early generations EGFR TKIs.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Acknowledgment

We would like to acknowledge NIH/NCI grant support R01CA224306 (to GKP and APS) and R01CA175772 (to APS).

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
 > References Top

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  [Figure 1], [Figure 2], [Figure 3], [Figure 4]



 

 
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