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Vol.52 No.3 contents

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- Original Article -

Clinical Significance of T790M After Acquiring Resistance to Gefitinib or Erlotinib in Non-small Cell Lung Cancer Patients with Epidermal Growth Factor Receptor Gene Mutation

Kazutoshi Isobe¹, Yoshinobu Hata², Keita Sato¹, Go Sano¹, Keishi Sugino¹, Susumu Sakamoto¹, Yujiro Takai¹, Kazutoshi Shibuya³, Keigo Takagi², Sakae Homma^1
1Department of Respiratory Medicine, ²Department of Chest Surgery, ³Department of Surgical Pathology, Toho University Omori Medical Center, Japan

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Objective. To clarify the usefulness of assessing T790M status in non-small cell lung cancer patients with epidermal growth factor receptor (EGFR) gene mutations at the time of acquiring epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI) resistance. Methods. Of 93 primary non-small cell lung cancer patients with EGFR mutations at the primary site treated in our institution over the last 6 years, 16 were assessed for the T790M mutation. The location and method of detecting T790M, frequency of this mutation, and response to a second EGFR-TKI were retrospectively analyzed. Results. The localization of EGFR mutations in the primary site was G719C in 1, G719C+L858R in 1, exon 19 deletion in 6, and L858R in 8, respectively. Locations of T790M were neck lymph nodes in 4 patients, mediastinal lymph node in 1, pleural effusion in 6, cerebrospinal fluid in 1, and lung tumor in 4. T790M was detected in 6 out of 16 cases (38%). The same EGFR mutations as in the primary site were detected in the other 10 cases. Eleven patients were treated with readministration of EGFR-TKI. Cases without T790M (n=8) showed significantly longer progression-free survival (PFS) than those with T790M (n=3) (median PFS: 15.0 months vs. 1.0 month, p=0.009). Conclusions. Screening for T790M in non-small cell lung cancer at the time of acquiring EGFR-TKI resistance is useful for selecting patients who will respond to EGFR-TKI readministration.
key words: Non-small cell lung cancer, Epidermal growth factor receptor gene mutation, Resistant mutation T790M, EGFR tyrosine kinase inhibitor

Received: January 11, 2012
Accepted: May 21, 2012

JJLC 52 (3): 279-283, 2012