Purpose: All patients with EGF receptor ( EGFR )–mutant lung cancers eventually develop acquired resistance to EGFR tyrosine kinase inhibitors (TKI). Smaller series have identified various mechanisms of resistance, but systematic evaluation of a large number of patients to definitively establish the frequency of various mechanisms has not been conducted. Experimental Design: Patients with lung adenocarcinomas and acquired resistance to erlotinib or gefitinib enrolled onto a prospective biopsy protocol and underwent a rebiopsy after the development of acquired resistance. Histology was reviewed. Samples underwent genotyping for mutations in EGFR, AKT1, BRAF, ERBB2, KRAS, MEK1, NRAS and PIK3CA , and FISH for MET and HER2 . Results: Adequate tumor samples for molecular analysis were obtained in 155 patients. Ninety-eight had second-site EGFR T790M mutations [63%; 95% confidence interval (CI), 55%–70%] and four had small cell transformation (3%, 95% CI, 0%–6%). MET amplification was seen in 4 of 75 (5%; 95% CI, 1%–13%). HER2 amplification was seen in 3 of 24 (13%; 95% CI, 3%–32%). We did not detect any acquired mutations in PIK3CA, AKT1, BRAF, ERBB2, KRAS, MEK1 , or NRAS (0 of 88, 0%; 95% CI, 0%–4%). Overlap among mechanisms of acquired resistance was seen in 4%. Conclusions: This is the largest series reporting mechanisms of acquired resistance to EGFR-TKI therapy. We identified EGFR T790M as the most common mechanism of acquired resistance, whereas MET amplification, HER2 amplification, and small cell histologic transformation occur less frequently. More comprehensive methods to characterize molecular alterations in this setting are needed to improve our understanding of acquired resistance to EGFR-TKIs. Clin Cancer Res; 19(8); 2240–7. ©2013 AACR .

https://clincancerres.aacrjournals.org/content/clincanres/19/8/2240.full.pdf

Analysis of Tumor Specimens at the Time of Acquired Resistance to EGFR-TKI Therapy in 155 Patients with EGFR-Mutant Lung Cancers

Screening for Epidermal Growth Factor Receptor Mutations in Lung Cancer

All patients with metastatic lung, colorectal, pancreatic or head and neck cancers who initially benefit from epidermal growth factor receptor (EGFR)-targeted therapies eventually develop resistance. An increasing understanding of the number and complexity of resistance mechanisms highlights the Herculean challenge of killing tumors that are resistant to EGFR inhibitors. Our growing knowledge of resistance pathways provides an opportunity to develop new mechanism-based inhibitors and combination therapies to prevent or overcome therapeutic resistance in tumors. We present a comprehensive review of resistance pathways to EGFR-targeted therapies in lung, colorectal and head and neck cancers and discuss therapeutic strategies that are designed to circumvent resistance.

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The quest to overcome resistance to EGFR-targeted therapies in cancer

Non-small cell lung cancer (NSCLC) patients with activating epidermal growth factor receptor (EGFR) mutations initially respond to first generation reversible EGFR tyrosine kinase inhibitors. However, clinical efficacy is limited by acquired resistance, frequently driven by the EGFR T790M mutation. CO-1686 is a novel, irreversible and orally delivered kinase inhibitor that specifically targets the mutant forms of EGFR including T790M while exhibiting minimal activity towards the wild-type (WT) receptor. Oral administration of CO-1686 as single agent induces tumor regression in EGFR mutated NSCLC tumor xenograft and transgenic models. Minimal activity of CO-1686 against the WT EGFR receptor was observed. In NSCLC cells with acquired resistance to CO-1686 in vitro, there was no evidence of additional mutations or amplification of the EGFR gene, but resistant cells exhibited signs of epithelial-mesenchymal transition (EMT) and demonstrated increased sensitivity to AKT inhibitors. These results suggest CO-1686 may offer a novel therapeutic option for patients with mutant EGFR NSCLC.

https://cancerdiscovery.aacrjournals.org/content/candisc/3/12/1404.full.pdf

Discovery of a Mutant-Selective Covalent Inhibitor of EGFR that Overcomes T790M-Mediated Resistance in NSCLC

Lung cancer with epidermal growth factor receptor (EGFR)-activating mutations responds favorably to the EGFR tyrosine kinase inhibitors gefitinib and erlotinib. However, 25% to 30% of patients with EGFR-activating mutations show intrinsic resistance, and the responders invariably acquire resistance to gefitinib. Here, we showed that hepatocyte growth factor (HGF), a ligand of MET oncoprotein, induces gefitinib resistance of lung adenocarcinoma cells with EGFR-activating mutations by restoring the phosphatidylinositol 3-kinase/Akt signaling pathway via phosphorylation of MET, but not EGFR or ErbB3. Strong immunoreactivity for HGF in cancer cells was detected in lung adenocarcinoma patients harboring EGFR-activating mutations, but no T790M mutation or MET amplification, who showed intrinsic or acquired resistance to gefitinib. The findings indicate that HGF-mediated MET activation is a novel mechanism of gefitinib resistance in lung adenocarcinoma with EGFR-activating mutations. Therefore, inhibition of HGF-MET signaling may be a considerable strategy for more successful treatment with gefitinib.

Hepatocyte growth factor induces gefitinib resistance of lung adenocarcinoma with epidermal growth factor receptor-activating mutations

Purpose: In epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) therapy for lung cancer patients, acquired resistance develops almost inevitably and this limits the improvement in patient outcomes. EGFR T790M mutation and MET amplification are the two main mechanisms underlying this resistance, but the relationship between these two mechanisms is unclear. In this study, we explored their relationship using in vitro models and autopsy specimens. Experimental Design: Erlotinib-resistant HCC827 (HCC827ER) cells were developed by chronic exposure to erlotinib at increasing concentrations. HCC827EPR cells were also developed by chronic exposure to erlotinib in the presence of PHA-665,752 (a MET TKI). The erlotinib-resistant mechanisms of these cells were analyzed. In addition, 33 autopsy tumor samples from 6 lung adenocarcinoma patients harboring multiple gefitinib-refractory tumors were analyzed. Results: HCC827ER developed MET amplification, and clinically relevant resistance occurred at ≥4-fold MET gene copy number gain (CNG). By contrast, HCC827EPR developed T790M without MET CNG. Of six patients harboring gefitinib-refractory tumors, three exhibited T790M only, one exhibited MET amplification only, and the other two exhibited T790M and/or MET amplification depending on the lesion sites. In these gefitinib-refractory tumors, T790M developed in 93% (14 of 15) of tumors without MET gene CNGs, in 80% (4 of 5) of tumors with moderate MET gene CNGs ( MET amplification (≥4-fold). Conclusions: These results indicate a reciprocal and complementary relationship between T790M and MET amplification and the necessity of concurrent inhibition of both for further improving patient outcomes. Clin Cancer Res; 16(22); 5489–98. ©2010 AACR.

https://clincancerres.aacrjournals.org/content/clincanres/16/22/5489.full.pdf

Reciprocal and Complementary Role of MET Amplification and EGFR T790M Mutation in Acquired Resistance to Kinase Inhibitors in Lung Cancer

Efficacy of Erlotinib for Brain and Leptomeningeal Metastases in Patients with Lung Adenocarcinoma Who Showed Initial Good Response to Gefitinib

Purpose
A paravertebral block (PVB) given via the surgical field can be safer and technically simpler than an epidural block (EP) for postoperative pain control. We conducted this clinical trial to confirm the effectiveness of PVB after thoracotomy.

Paravertebral block via the surgical field versus epidural block for patients undergoing thoracotomy: a randomized clinical trial

Clinicopathological features of small-sized non-small cell lung cancer with mediastinal lymph node metastasis

Objective
We previously reported the noninferiority of paravertebral block (PVB) to epidural block. In this study, we assessed whether PVB via an intrathoracic approach was also safe for the patients ineligible for epidural block because of, for example, anticoagulation or antiplatelet therapy.

Tatsuya Katayama

Papers

Reciprocal and Complementary Role of MET Amplification and EGFR T790M Mutation in Acquired Resistance to Kinase Inhibitors in Lung Cancer

Efficacy of Erlotinib for Brain and Leptomeningeal Metastases in Patients with Lung Adenocarcinoma Who Showed Initial Good Response to Gefitinib

Paravertebral block via the surgical field versus epidural block for patients undergoing thoracotomy: a randomized clinical trial

Clinicopathological features of small-sized non-small cell lung cancer with mediastinal lymph node metastasis

Safety of the paravertebral block in patients ineligible for epidural block undergoing pulmonary resection.