The mechanism of acquired resistance to irreversible EGFR tyrosine kinase inhibitor-afatinib in lung adenocarcinoma patients

// Shang-Gin Wu 1, 2 , Yi-Nan Liu 3 , Meng-Feng Tsai 4 , Yih-Leong Chang 5 , Chong-Jen Yu 2, 3 , Pan-Chyr Yang 2, 3 , James Chih-Hsin Yang 6 , Yueh-Feng Wen 7 , Jin-Yuan Shih 2, 3 1 Department of Internal Medicine, National Taiwan University Hospital Yun-Lin Branch, Yun-Lin, Taiwan 2 Graduate Institute of Clinical Medicine, College of Medicine, National Taiwan University, Taipei, Taiwan 3 Department of Internal Medicine, National Taiwan University Hospital, and College of Medicine, National Taiwan University, Taipei, Taiwan 4 Department of Molecular Biotechnology, Da-Yeh University, Chang-Hua, Taiwan 5 Department of Pathology, National Taiwan University Hospital, College of Medicine, National Taiwan University, Taipei, Taiwan 6 Department of Oncology, National Taiwan University Hospital, and Graduate Institute of Oncology, Cancer Research Center, National Taiwan University, Taipei, Taiwan 7 Department of Internal Medicine, National Taiwan University Hospital Hsinchu Branch, Hsinchu, Taiwan Correspondence to: Jin-Yuan Shih, e-mail: jyshih@ntu.edu.tw Keywords: lung adenocarcinoma, afatinib, T790M, acquired resistance, EGFR TKI Received: October 08, 2015      Accepted: January 23, 2016      Published: February 04, 2016 ABSTRACT Introduction: Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) are associated with favorable response in EGFR mutant lung cancer. Acquired resistance to reversible EGFR TKIs remains a significant barrier, and acquired EGFR T790M-mutation is the major mechanism. Second-generation irreversible EGFR TKI, afatinib, had also been approved for treating EGFR mutant lung cancer patients, but the mechanism of acquired resistance to afatinib has not been well studied. Results: Forty-two patients had tissue specimens taken after acquiring resistance to afatinib. The sensitizing EGFR mutation were all consistent between pre- and post-afatinib tissues. Twenty patients (47.6%) had acquired T790M mutation. T790M rate was not different between first-generation EGFR TKI-naïve patients (50%) and first-generation EGFR TKI-treated patients (46.4%) ( p = 0.827). No clinical characteristics or EGFR mutation types were associated with the development of acquired T790M. No other second-site EGFR mutations were detected. There were no small cell or squamous cell lung cancer transformation. Other genetic mutations were not identified in PIK3CA , BRAF , HER2 , KRAS , NRAS , MEK1 , AKT2 , LKB1 and JAK2 . Methods: Afatinib-prescription record of our department of pharmacy from January 2007 and December 2014 was retrieved. We investigated patients with tissue specimens available after acquiring resistance to afatinib. Enrolled patients should have partial response or durable stable disease of treatment response to afatinib. Various mechanisms of acquired resistance to first-generation EGFR TKIs were evaluated. Histology and cytology were reviewed. EGFR , PIK3CA , BRAF , HER2 , KRAS , NRAS , MEK1 , AKT2 , LKB1 and JAK2 genetic alterations were evaluated by sequencing. Statistical analysis was performed using Chi-square test and Kaplan-Meier method. Conclusions: T790M was detected in half of the lung adenocarcinoma after acquiring resistance to afatinib. T790M is still the major acquired resistance mechanism. First-generation EGFR TKI exposure did not influence the prevalence of T790M in lung cancer acquired resistance to afatinib.