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W. Liu



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    MA 06 - Lung Cancer Biology I (ID 660)

    • Event: WCLC 2017
    • Type: Mini Oral
    • Track: Biology/Pathology
    • Presentations: 1
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      MA 06.09 - Detection of EGFR T790M Mutations by Four Testing Platforms in ctDNA from Chinese Patients with Advanced NSCLC (ID 8615)

      15:45 - 17:30  |  Author(s): W. Liu

      • Abstract
      • Presentation
      • Slides

      Background:
      Osimertinib is a third-generation EGFR tyrosine kinase inhibitor (EGFR-TKI) targeting sensitizing mutations and T790M mutation, which causes ~60% of acquired resistance after first-line TKI treatment. T790M testing provides guidance for second-line treatment decisions. This study evaluated four T790M detection platforms using plasma circulating tumor DNA (ctDNA).

      Method:
      ADELOS is a multicentre, open-label, single-arm study (NCT 02997501) of Chinese patients with advanced non-small cell lung cancer (NSCLC) and progression on previous EGFR-TKI treatment. Plasma ctDNA testing for T790M was performed by Cobas[®] real-time polymerase chain reaction (PCR), super amplification refractory mutation system (Super-ARMS) PCR, capture-based next-generation sequencing (NGS, 168 gene panel), and QuantStudio3D digital PCR (3D dPCR). T790M-positive patients detected by these platforms received osimertinib 80 mg/day orally until progression. Matched tissue re-biopsy samples were also tested by Cobas[®] or NGS. The primary objectives were to evaluate concordance between the Cobas[®] test and the other three platforms and to assess the efficacy of osimertinib in ctDNA T790M-positive patients.

      Result:
      Of 256 patients enrolled, 181 were ctDNA T790M-positive, among which 167 received osimertinib monotherapy. T790M plasma positive rate was from 37.4% to 63.5% (Cobas[®]< Super-ARMS90% for all three platforms. Specificity was between 53% (3D dPCR) and 89% (Super-ARMS). Compared with paired tissue testing results (n=73), NGS showed the highest concordance and sensitivity, while Cobas[® ]showed the highest specificity (Table 1). Table 1. Comparison of different platforms for T790M detection

      Cobas[®] PCR n=254 Super-ARMS PCR n=256 NGS n=256 3D dPCR n=255
      T790M detected, n (%) 95 (37.4) 108 (42.2) 138 (53.9) 162 (63.5)
      Comparison vs Cobas plasma test (n=254)
      Concordance %, (95% CI) -- 91.3 (87.2, 94.5) 82.7 (77.5, 87.1) 66.8 (60.6, 72.6)
      Sensitivity %, (95% CI) -- 94.7 (88.1, 98.3) 98.9 (94.3, 100.0) 90.5 (82.8, 95.6)
      Specificity %, (95% CI) -- 89.3 (83.4, 93.6) 73.0 (65.3, 79.7) 52.5 (44.4, 60.5)
      Comparison vs Tissue (n=73)
      Concordance %, (95% CI) 67.1 (55.1, 77.7) 64.4 (52.3, 75.3) 69.9 (58.0, 80.1) 61.6 (49.5, 72.8)
      Sensitivity %, (95% CI) 57.1 (42.2, 71.2) 61.2 (46.2, 74.8) 71.4 (56.7, 83.4) 69.4 (54.6, 81.7)
      Specificity %, (95% CI) 87.5 (67.6, 97.3) 70.8 (48.9, 87.4) 66.7 (44.7, 84.4) 45.8 (25.6, 67.2)


      Conclusion:
      Super-ARMS showed highest concordance and NGS showed highest sensitivity compared with Cobas® plasma T790M testing. Concordance and specificity of 3D dPCR was lower using other ctDNA tests or tissue as reference. Subsequent osimertinib treatment in these patients will justify the effectiveness of T790M testing by different technologies.

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