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T.K. Lim



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    OA 09 - EGFR TKI Resistance (ID 663)

    • Event: WCLC 2017
    • Type: Oral
    • Track: Advanced NSCLC
    • Presentations: 1
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      OA 09.07 - Clonality of c-MET Copy Number Gain as a Determinant of Primary TKI Resistance in EGFR-Mutant NSCLC (ID 8887)

      12:05 - 12:15  |  Author(s): T.K. Lim

      • Abstract
      • Presentation
      • Slides

      Background:
      cMET activation is a valid mechanism of secondary TKI resistance in EGFR mutation-positive (EGFR-M+) NSCLC. However, its role in the treatment-naïve setting remains unclear. We sought to ascertain the prevalence and clinical impact of co-existing cMET copy number gain(CNG) in TKI-naïve early-stage and metastatic EGFR-M+ NSCLC.

      Method:
      Multi-region SNP array analysis (n=59 sectors) was performed on 13 early-stage resected EGFR-M+ NSCLC. cMET FISH was performed in a separate cohort of 206 metastatic treatment-naïve EGFR-M+ patients, all of whom were treated with first-line EGFR TKIs. We defined cMET-high as CNG≥5 copies, with an additional criteria of MET:CEP7 ratio >2.0 for amplification. Time-to-treatment failure(TTF) in patients cMET-high/low was estimated by Kaplan-Meier method and compared using log-rank test. A cell line from a cMET-high patient exhibiting primary TKI resistance was established.

      Result:
      Relative to median ploidy across sectors, 7/13(53.8%) early-stage EGFR-M+ tumors showed cMET CNG in at least one sector, with majority displaying(n=6/7) copy number intra-tumor heterogeneity. In the metastatic cohort, 55/206 patients (26.7%) were found to be cMET-high at diagnosis: 6(10.9%) had MET amplification, 49(89.1%) MET polysomy, with the following distribution: 5-6 copies(n=11), 6-8 copies(n=32), and >8 copies(n=12). We next evaluated clinical outcomes stratified by MET-high v low: median TTF was 14.7m(12.2–NE) vs 14.6m(12.7–16.5), p=0.985 respectively, with no significant difference in response rates(RR) to EGFR TKI (66.7%v73.7%; p=0.940). Further stratification by level of CNG did not reveal any differences in RR (5-6 copies:75.0%, 6-8 copies:63.0%, >8 copies:71.4%; p=0.868). In MET-high amplified group, only 2/6 (33.3%) had a partial response to EGFR TKI. In the cohort with suboptimal TKI response (PFS<6m, n=22), we did not observe significant enrichment for MET-high, relative to rest of the cohort (36.4%v25.5%, p=0.278). Finally, in 6 patients with progressive disease within 4 weeks of initiating EGFR TKI, 2/6(33.3%) were MET-high. In a cell line model derived from a MET-high patient (L858R, cMET:7.3 copies) genomic profiling of cell colonies revealed clonal cMET CNG and subclonal EGFR, with the patient demonstrating clinical response to crizotinib.

      Conclusion:
      Although up to 26% of TKI-naïve EGFR-M+ NSCLC harbor high cMET CNG by FISH, this occurs on the background of a highly variegated copy number landscape. cMET CNG alone does not significantly impact clinical outcomes to EGFR TKI, with the exception of one patient with a clonal cMET-driven tumor. Our data challenges the utility of arbitrary copy number thresholds to define clinically relevant MET pathway dysregulation and underscores the importance of targeting dominant truncal drivers.

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