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Q. Zhang



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    JCHS - Joint IASLC - Chinese Society for Clinical Oncology - Chinese Alliance Against Lung Cancer Session (ID 239)

    • Event: WCLC 2015
    • Type: Joint Chinese/ English Session
    • Track: Other
    • Presentations: 1
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      JCHS.08 - Role of T790M Mutation in EGFR-TKI Rechallenge for Patients with EGFR-Mutant Advanced Non-Small Cell Lung Cancer (ID 3525)

      09:25 - 09:35 AM  |  Author(s): Q. Zhang

      • Abstract
      • Presentation
      • Slides

      Background:
      Epidermal growth factor receptor (EGFR) exon 20 T790M mutation may have a predictive role before EGFR-tyrosine kinase inhibitors (TKIs) treatment and it also might have a prognostic role after acquired resistance to EGFR-TKIs. However, its role in EGFR-TKI rechallenge after failure of initial EGFR-TKIs in EGFR-mutant advanced non-small cell lung cancer (NSCLC) remains unknown.

      Methods:
      We retrospectively evaluated the clinical course of 515 EGFR-mutant advanced NSCLC patients who received first generation EGFR-TKIs (gefitinib or erlotinib) from December 2009 to November 2014 at Guangdong General Hospital. Of these 515 patients, 65 patients recieved same EGFR-TKI rechallenge, including 51 patients who underwent rebiopsy and secondary EGFR mutation detection after failure of initial EGFR-TKIs. EGFR detection was performed by Sanger sequencing or Amplification Refractory Mutation System (ARMS) methods. Progression-free survival (PFS) and overall survival (OS) were both calculated from commencement of EGFR-TKI rechallenge. Survival data were analyzed using the Kaplan-Meier method and log-rank test.

      Results:
      EGFR activating mutations still existed in all the 51 patients who received rebiopsy and 18 patients were with T790M mutation while 33 patients were without T790M. The median PFS for the T790M+ and T790M- groups were 1.8 months (95%CI 1.180~2.420) and 2.0 months (95%CI 1.100~2.900), respectively (P=0.261). The median OS for the two groups were 7.7 months (95%CI 6.548~8.852) and 6.8 months (95%CI 4.730~8.870), respectively (P=0.565). No statistical difference was found in PFS or OS between two groups(Figure 1). Fig 1. Kaplan-Meier curves of patients in two groups. (A)Progression-free survival. (B) Overall survival.

      Conclusion:
      EGFR T790M mutation is neither a predictive nor a prognostic factor for first generation EGFR-TKI rechallenge in EGFR-mutant advanced NSCLC patients, indicating that whether T790M occurs or not, same EGFR-TKI rechallenge could not be recommended as a good strategy to overcome the resistance to first generation EGFR-TKIs.

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    ORAL 16 - Clinical Care of Lung Cancer and Advanced Biopsies (ID 115)

    • Event: WCLC 2015
    • Type: Oral Session
    • Track: Treatment of Advanced Diseases - NSCLC
    • Presentations: 1
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      ORAL16.07 - Intratumor Heterogeneity of EGFR Activating Mutations Analyzed in Single Cancer Cells in Advanced NSCLC Patients (ID 2311)

      11:50 - 12:01 PM  |  Author(s): Q. Zhang

      • Abstract
      • Presentation
      • Slides

      Background:
      Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) can achieve dramatic response in EGFR activating mutation positive lung cancer patients. However, the duration of treatment is quite different. Some patients experienced longer progression-free survival (PFS) of more than 1 year, whereas some had PFS of shorter than 6 months. Our previous study showed that the relative EGFR mutation abundance in tumor tissues could predict benefit from EGFR-TKIs treatment. However, it still remains controversial whether the intratumor heterogeneity of EGFR activating mutation exists. This study explored the intratumor heterogeneity of EGFR activating mutation at the level of single cancer cell.

      Methods:
      Single H1975 cells which harbor EGFR exon 21 L858R mutation were isolated by flow cytometry (FCM). The whole DNA extracted from a single cell was submitted to perform nested polymerase chain reaction (PCR) amplification of EGFR exon 21. The amplified products from nested PCR were sequenced to evaluate the feasibility of single-cell analysis for EGFR exon 21. Then, six patients diagnosed with lung adenocarcinoma whose fresh frozen specimens harbored EGFR exon 21 mutation tested by direct sequencing were chosen. All of them received gefitnib treatment and the PFS of three patients was longer than 14 months (Group A) while the PFS of other three patients was shorter than 6 months (Group B). By using the established method based on single H1975 cells, EGFR exon 21 mutational status was analyzed in single tumor cells which were captured from tumor sample by Laser Capture Microdissection (LCM). At least 20 tumor cells were captured from each tumor sample. X[2] test was used to compare the amplification rate of nested PCR and EGFR mutational rate between the two groups.

      Results:
      A total of 104 individual H1975 cells were obtained to detect EGFR exon 21 mutational status through the application of single-cell nested PCR. The amplification rate and allele drop-out rate were 96.2% and 7.0%. A total of 135 tumor cells from six samples were captured. The amplification rate of nested PCR was 84.3% (59/70) in Group A and 93.8% (61/65) in Group B. There was no statistical difference between the two groups (X[2] =3.119, P=0.077). The mutational rate of EGFR exon 21 L858R was 89.5% (17/19), 89.5% (17/19), and 81.0% (17/21) in the three patients in Group A and 72.2% (13/18), 68.4% (15/22), and 66.7% (14/21) in the three patients in Group B respectively. The total mutational rate was 86.4%(51/59)in Group A, which was significantly higher than the total mutational rate 68.9%(42/61)in Group B (X[2] =5.321, P=0.021).

      Conclusion:
      It is feasible to perform EGFR mutation detection in single cancer cells. The intratumoral heterogeneity of EGFR activating mutation in lung adenocarcinoma does exist based on the analysis in single cancer cells and the abundance of EGFR activating mutation is relevant to the benefit from EGFR-TKIs treatment.

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