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Jan H. Von Der Thüsen



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    P2.13 - Targeted Therapy (Not CME Accredited Session) (ID 962)

    • Event: WCLC 2018
    • Type: Poster Viewing in the Exhibit Hall
    • Track:
    • Presentations: 1
    • Moderators:
    • Coordinates: 9/25/2018, 16:45 - 18:00, Exhibit Hall
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      P2.13-28 - Comparison of ddPCR and NGS in Liquid Biopsy to Pathology Results in EGFR-Mutated NSCLC (ID 13889)

      16:45 - 18:00  |  Author(s): Jan H. Von Der Thüsen

      • Abstract
      • Slides

      Background

      In the blood of EGFR-mutated NSCLC patients, primary activating mutations as well as the resistance mutation T790M can be detected in ctDNA (liquid biopsy). Several methods have been developed for this purpose but techniques are still evolving. We compared two tests (BioRad digital droplet PCR (ddPCR) and IonTorrent/Oncomine next generation sequencing (NGS)) for ctDNA primary activating EGFR mutations and T790M to results of pathological investigation of a tissue biopsies or pleural fluid.

      a9ded1e5ce5d75814730bb4caaf49419 Method

      We collected the data on liquid biopsies performed on EGFRm+ NSCLC patients from November 2016 untill February 2018 at the Erasmus MC. In this study we analyzed all liquid biopsies from patients with EGFR mutations at baseline or after progression from whom also pathology results in the same time frame of treatment were available.

      Liquid biopsy results obtained from the two methods were compared to each other as well as to the pathology results. Cohen’s kappa was calculated as measure of agreement.

      4c3880bb027f159e801041b1021e88e8 Result

      In total, 29 out of 123 patients (24%) did meet the criteria and were included in our study.

      Concordance for the detection of the primary activating mutation between pathology results and blood was 66% for the BioRad ddPCR and 83% for the IonTorrent/Oncomine NGS (n=29). Concordance for the detection of p.T790M between pathology results and blood was 76% for both ddPCR and NGS (κ=0.51, n=29). In 5 patients (17%), p.T790M was detected by pathology results but not in cfDNA. In 2 patients (7%), p.T790M was detected in blood but not in the pathology specimen.

      Concordance between ddPCR and NGS on blood for the primary activating EGFR mutation was 83% (κ=0.57, n=29) and for p.T790M detection 93% (κ=0.86, n=29).

      8eea62084ca7e541d918e823422bd82e Conclusion

      Detection of mutations in plasma show reasonable to high concordance with tissue biopsy. The method of testing defines the extent of the number of tested mutations and therefore the height of concordance. NGS seems to upscale the concordance of detection of the primary mutation due to examination of a broader panel of available mutations (in ddPCR only exon 19 deletions and exon 21 p.L858R are tested), but is comparable to ddPCR on the level of a specific mutation in the panel (p.T790M).

      Discrepant results between pathology specimens and liquid biopsy remain a difficult issue for clinical practice.

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