Clinical Research Papers:
Clinical significance of repeat rebiopsy in detecting the EGFR T790M secondary mutation in patients with non-small cell lung cancer
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Eiki Ichihara1, Katsuyuki Hotta2, Toshio Kubo3, Tsukasa Higashionna4, Kiichiro Ninomiya1, Kadoaki Ohashi5, Masahiro Tabata3, Yoshinobu Maeda5 and Katsuyuki Kiura1
1Department of Allergy and Respiratory Medicine, Okayama University Hospital, Okayama, Japan
2Center for Innovative Clinical Oncology, Okayama University Hospital, Okayama, Japan
3Center for Clinical Oncology, Okayama University Hospital, Okayama, Japan
4Department of Clinical Pharmaceutics, Okayama University Hospital, Okayama, Japan
5Department of Hematology, Oncology and Respiratory Medicine, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan
Eiki Ichihara, email: [email protected]
Keywords: EGFR; lung cancer; osimertinib; rebiopsy; T790M
Received: March 09, 2018 Accepted: June 12, 2018 Published: June 29, 2018
Background: Osimertinib is an essential drug to treat non-small-cell lung cancer (NSCLC) harboring the epidermal growth factor receptor (EGFR) T790M mutation, and rebiopsy is necessary to detect this mutation. However, the significance of repeat rebiopsy in NSCLC patients whose first rebiopsy was T790M-negative remains unclear. We used a retrospective cohort to clarify this issue.
Methods: We reviewed the medical records of patients with NSCLC harboring EGFR mutations who underwent EGFR tyrosine kinase inhibitor (TKI) treatment at Okayama University Hospital between January 2015 and January 2017.
Results: Of 102 patients with EGFR-mutant NSCLC, 55 underwent rebiopsy after acquired resistance to prior EGFR TKIs. Pre-existing activating EGFR mutations were found in all 55 rebiopsied samples. Of the 55 samples, 25 were T790M-positive (45%). Among the remaining 30 patients (T790M-negative on the first rebiopsy), 21 underwent additional rebiopsies following interval therapy. Of the 21 patients, 11 were T790M-positive on the second rebiopsy and 1 on the third. We also evaluated the efficacy of osimertinib in patients who needed a repeat rebiopsy to detect the T790M mutation. Osimertinib showed good activity with an objective response rate of 50%.
Conclusions: Repeat rebiopsy increases the ability to detect a secondary mutation (T790M) in EGFR.
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