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Congying Xie



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    MA16 - Novel Mechanisms for Molecular Profiling (ID 917)

    • Event: WCLC 2018
    • Type: Mini Oral Abstract Session
    • Track: Advanced NSCLC
    • Presentations: 1
    • Moderators:
    • Coordinates: 9/25/2018, 13:30 - 15:00, Room 203 BD
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      MA16.06 - EGFR Clonality and Tumor Mutation Burden (TMB) by Circulating Tumor DNA (ctDNA) Sequencing in Advanced Non-Small Cell Lung Cancer (NSCLC) (ID 13146)

      14:05 - 14:10  |  Author(s): Congying Xie

      • Abstract
      • Presentation
      • Slides

      Background

      TKI has significantly improved survival time of NSCLC pts with sensitive mutation. However, pts present different outcome while receiving TKI treatment. We conduct a prospective multicenter clinical trial to determine whether clonality of sensitive mutation is related to the efficacy of TKI. We also evaluate the consistency of TMB between tissue and blood in this cohort.

      a9ded1e5ce5d75814730bb4caaf49419 Method

      Paired tumor and plasma samples at diagnosis were obtained from systemic treatment naïve pts with advanced NSCLC. DNA was sequenced by target-capture deep sequencing of 1021 previously annotated genes related to solid tumors. Clonal EGFR mutation was defined if EGFR mutation was in the cluster with the highest mean variated allele frequency with PyClone, and otherwise subclonal EGFR mutation. TMB of tissue (tTMB) and blood (bTMB) analysis interrogated single nucleotide variants, small insertion and deletion, with VAF ≥3 % and ≥0.5 %, respectively. TMB-high pts were identified with ≥9 mut/MB (upper quartile of data from geneplus).

      4c3880bb027f159e801041b1021e88e8 Result

      During February 2017 to April 2018, 127 advanced NSCLC pts were enrolled from 9 centers. A total of 653 somatic variations were detected in tissues. Mutations occurred most frequently in EGFR (57 %), TP53 (54 %), KRAS (9 %), ALK (8 %). In matched plasma, 405 (62 %) tumor-derived mutations were detected by pan-caner panel sequencing. A total of 90 EGFR mutations were detected in 73 pts, most of which occurred in tyrosine kinase domain (L858R, 41%; Ex19del, 33%). Most EGFR mutation were clonal in tissue and plasma, with a consistence of 83 % in paired samples. In addition, bTMB was significantly correlated to tTMB (Pearson r= 0.85, p-value= 1.8e-30), with a consistence of 89 %. Interestingly, high TMB was observed in a small fraction of patients (8 %) with driver mutations, such as mutations in EGFR, ALK fusion, ERBB2 and PIK3CA.

      8eea62084ca7e541d918e823422bd82e Conclusion

      Deep sequencing with the pan-cancer panel can effectively detect mutations and evaluate TMB in both tissue and blood with high consistence. EGFR mutations can be clonal or subclonal in both tissue and blood. Prospective multicenter study is ongoing to determine the EGFR clonality as a predictive factor for the TKI efficacy in NSCLC (TRACELib-NSCLC, NCT03059641).

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