Author of

• 28971

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  Lunch & Poster Display session (ID 58)

  • Event: ELCC 2019
  • Type: Poster Display session
  • Track:
  • Presentations: 2
  • Moderators:
  • Coordinates: 4/11/2019, 12:30 - 13:00, Hall 1

  • 29068

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    134P - Mutational spectrum of acquired resistance to reversible versus irreversible EGFR tyrosine kinase inhibitors (ID 297)

    12:30 - 13:00  |  Author(s): Sabine Merkelbach-Bruse
    • Abstract

    Background
    

    Mutational spectrum of acquired resistance to reversible versus irreversible EGFR tyrosine kinase inhibitors Over the past years, EGFR tyrosine kinase inhibitors (TKI) revolutionized treatment response. 1st-generation (reversible) EGFR TKI later the 2nd –generation irreversible EGFR TKI Afatinib was aimed to improve treatment response. Nevertheless, diverse resistance mechanisms develop within the first year of therapy. Here, we evaluate the prevalence of acquired resistance mechanisms towards reversible and irreversible EGFR TKI.

    a9ded1e5ce5d75814730bb4caaf49419 Methods
    

    Rebiopsies of patients after progression to EGFR TKI therapy (>6months) were targeted to histological and molecular analysis. Multiplexed targeted sequencing (NGS) was conducted to identify acquired resistance mutations (e.g. EGFR p.T790M). Further, Fluorescence in situ hybridisation (FISH) was applied to investigate the amplification status of bypass mechanisms like, MET or HER2.

    20c51b5f4e9aeb5334c90ff072e6f928 Results
    

    123 rebiopsy samples of patients that underwent firts-line EGFR TKI therapy ( PFS >6months) were histologically and molecularly profiled upon clinical progression. The EGFR p.T790M mutation ist the major mechanism of acquired resistance in patients treated with reversible as well as irreversible EGFR TKI. Nevertheless a statistically significant difference for the acquisition of T790M mutation has been idientified: 45% of afatinib- vs 65% of reversible EGFR TKI treated patients developed a T790M mutation (p-value 0.02). Progression free survival (PFS) was comparable in patients treated with irreversible EGFR irrespective of the sensitising primary mutation or the acquisition of p.T790M.

    fd69c5cf902969e6fb71d043085ddee6 Conclusions
    

    The EGFR p.T790M gatekeeper mutation ist he most prominent mechanism of resistance to reversible and irreversible EGFR TKI therapy. Nevertheless there is a statistically significant prevalence of p.T790M acquisition between the two types of TKI, which might be of importance for clinical therapy decision.

    b651e8a99c4375feb982b7c2cad376e9 Legal entity responsible for the study
    

    The authors.

    213f68309caaa4ccc14d5f99789640ad Funding
    

    Boehringer Ingelheim.

    682889d0a1d3b50267a69346a750433d Disclosure
    

    S. Wagener-Ryczek: Honoraria: Boehringer Ingelheim. C. Heydt: Honoraria: AstraZeneca, BMS, Illumina. S. Michels: Honoraria: Novartis, Pfizer, AstraZeneca, Boehringer Ingelheim; Advisory roles: Boehringer Ingelheim, Pfizer; Research funding: Pfizer, Novartis, BMS; Travel support/accommodations: Novartis. J. Fassunke: Honoraria, advisory role: AstraZeneca. M. Tiemann: Honoraria: Pfizer, Novartis, Roche. L. Heukamp: Co-founder: Neo New Oncology. J. Wolf: Honoraria: AstraZeneca, BMS, Clovis Oncology, Lilly, MSD, Novartis, Pfizer, Roche; Advisory roles: AstraZeneca, BMS, Clovis Oncology, Lilly, MSD, Novartis, Pfizer, Roche, Amgen. R. Buettner: Co-founder, Chief Scientific Officer: Targos Molecular Pathology; Honoraria: Roche, Pfizer, Novartis, AstraZeneca, Qiagen, MSD, BMS, Lilly. S. Merkelbach-Bruse: Honoraria: AstraZeneca; Advisory roles: AstraZeneca, Roche. All other authors have declared no conflicts of interest.

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    27P - Comparison of three different gene panels for determination of tumor mutational burden by next generation sequencing (ID 371)

    12:30 - 13:00  |  Author(s): Sabine Merkelbach-Bruse
    • Abstract

    Background
    

    The introduction of cancer immunotherapies has improved survival rates of certain groups of patients. According to first studies, that used whole exome sequencing, the accumulation of tumor neoantigens and therefore tumor mutational burden (TMB) could be used as molecular marker for prediction. In this study, large gene panel assays of different suppliers were tested on 28 DNA samples derived from formalin fixed, paraffin-embedded (FFPE) tumor tissue with regard to implementation in routine diagnostics.

    a9ded1e5ce5d75814730bb4caaf49419 Methods
    

    After DNA isolation the following kits of three different suppliers have been used for library preparation: A custom SureSelect^XTHS Target Assay (Agilent Technologies, Santa Clara, CA, USA), the NEOplus v2 RUO assay (New Oncology, Cologne, Germany) and the TruSight Oncology 500 kit (Ilumina, San Diego, CA, USA, TSO500) following manufacturers’ protocol. All assays were sequenced on the NextSeq 500 system (Illumina). For quality control the TapeStation 4200 System (Agilent Technologies) was used.

    20c51b5f4e9aeb5334c90ff072e6f928 Results
    

    All kits tested showed different final concentration after library preparation. Fragment sizes were as expected and libraries were suitable for sequencing. In terms of time needed for library preparation the NEOplus v2 RUO assay was the most laborious kit. The resulting TMB-scores showed similar picture for all kits and samples tested. For all panels access to the results of the sequenced genes and detected variants is possible. Data access differs between the developers in terms of availability and manageability. Since not all kits use unique molecular identifiers (UMI) the filtering capabilities are different.

    fd69c5cf902969e6fb71d043085ddee6 Conclusions
    

    In this study, three different gene panel assays for TMB-determination were tested. All panels provided a similar TMB-score for the analysed samples. In terms of usage and in respect of implementation in routine diagnostics, time and efficiency are the most important parameters. Here, the TSO500 kit and the SureSelect^XTHS Target Assay showed the best potential for the use in routine diagnostics.

    b651e8a99c4375feb982b7c2cad376e9 Legal entity responsible for the study
    

    The authors.

    213f68309caaa4ccc14d5f99789640ad Funding
    

    Has not received any funding.

    682889d0a1d3b50267a69346a750433d Disclosure
    

    C. Heydt: Honoraria: AstraZeneca, BMS, Illumina. S. Merkelbach-Bruse: Honoraria: AstraZeneca; Advisory role: AstraZeneca, Roche. All other authors have declared no conflicts of interest.

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