Author of

• 18974

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  P3.02 - Biology/Pathology (ID 620)

  • Event: WCLC 2017
  • Type: Poster Session with Presenters Present
  • Track: Biology/Pathology
  • Presentations: 1
  • Moderators:
  • Coordinates: 10/18/2017, 09:30 - 16:00, Exhibit Hall (Hall B + C)

  • 23992

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    P3.02-044 - Diagnosis and Monitoring of EGFR Mutation Status with cfDNA in Advanced NSCLC: A Prospective Single Institution Study in Asia (ID 9445)

    09:30 - 09:30  |  Author(s): H. Ho
    • Abstract

    Background:
    NSCLC patients in advanced stage with tumors that harbor EGFR sensitizing mutations are eligible for treatment with tyrosine kinase inhibitors (TKI) due to a high likelihood of response. The challenge with NSCLC is that often only small biopsy samples are available and when they are insufficient for molecular diagnostics, a repeat biopsy is not always possible and this results in delays in starting treatment. Molecular testing on circulating cell free DNA (cfDNA) from plasma is an alternative methodology that is readily applicable. We used the Roche cobas® EGFR Mutation Test V2 to diagnose (on tissue) and follow patients with EGFR sensitizing mutations to evaluate longitudinal changes in EGFR mutation status and SQI (Semi-quantitative Index) in plasma relative to standard of care for patients during TKI treatment. The sequential EGFR SQI values will be used to evaluate the relationship between molecular and clinical responses.
    
    Method:
    We included 60 patients (36 F/24 M) who had at least three follow up blood samples drawn post TKI treatment start. Ten ml of blood was collected in EDTA tubes from each subject at every visit. All patients had both tissue as well as baseline plasma EGFR results available. Serial follow up plasma samples were available on all patients. All subjects were treatment naïve, 80% (48/60) had no history of smoking and majority (45/60, 75%) presented with extra thoracic disease with clinical stages ranging between III-IV at diagnosis.
    
    Result:
    The L858R mutation was the most common EGFR mutation detected (58.3%) on the tissue followed by exon 19 deletion (35.0%). Two patients had dual mutations detected on tissue as well as in the baseline plasma. Plasma cfDNA analysis detected EGFR mutations in 78% of the baseline samples. Analysis of the serial plasma collected from patients who progressed while on 1[st] line TKI showed reappearance of the original EGFR sensitizing mutations with increasing SQI levels before emergence of a T790M mutation. T790M mutation was detected in 20.0% (12/60) of the patients on TKI treatment.
    
    Conclusion:
    This study clearly demonstrates that EGFR mutations can be reliably detected in plasma of NSCLC patients to confidently diagnose the presence of TKI resistance mutations using the Roche cobas® EGFR Mutation Test V2. Additionally, plasma SQI measurement can be used to monitor patients to detect the development of molecular TKI resistance. We will also show that serial measurement in the EGFR SQI can predict the relationship between molecular and clinical responses as well as tumor progression.