Author of

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  MA24 - Genomic Evolution, KEAP 3 and More Non-Coding RNA (ID 928)

  • Event: WCLC 2018
  • Type: Mini Oral Abstract Session
  • Track: Biology
  • Presentations: 1
  • Moderators:
  • Coordinates: 9/26/2018, 10:30 - 12:00, Room 205 BD

  • 26182

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    MA24.05 - Baseline Spatial Heterogeneity of T790M in Tyrosine Kinase Inhibitor Naïve EGFR-Mutant Lung Adenocarcinomas (ID 14171)

    11:00 - 11:05  |  Author(s): James Kuo
    • Abstract
    • Presentation
    • Slides

    Background
    

    Despite a good initial response, most epidermal growth factor receptor EGFR-mutant lung adenocarcinomas develop resistance after treatment with 1st and 2nd generation tyrosine kinase inhibitors (TKIs). Approximately 50-60% of resistance can be attributed to the EGFRT790M mutation, which provides a higher affinity ATP binding site that outcompetes TKIs and restore constitutive kinase function. Although classically thought of as de novoacquisition, the presence of T790M has been shown to exist in some tumors before TKI-therapy. Obtaining a spatial map of T790M in TKI-naïve tumors can provide insight into development of this type of resistance.

    a9ded1e5ce5d75814730bb4caaf49419 Method
    

    Eight cases of TKI-naive primary lung adenocarcinoma resections that were later found to be positive for T790M post-treatment with TKI were collected from 2004 to 2012. Initial pre-treatment tumor surgical resections were used for DNA extraction. Two tumor sections per case were divided into equal grid-like regions of approximately 8x8 mm². The number of grids ranged from 16 to 32 per case, based on tumor size (0.8 cm to 6.5 cm). Digital droplet polymerase chain reaction was used to genotype the sensitizing EGFR-mutations and T790M mutations at each region. Allelic frequencies (AF) of the mutations were measured. Recurrence free interval, defined as surgical resection date to date of recurrence detection, and total duration of TKI-therapy were extracted from medical records.

    4c3880bb027f159e801041b1021e88e8 Result
    

    All eight cases of TKI-naïve EGFR-mutant lung adenocarcinomas were positive for T790M at baseline. T790M tumor burden, defined as the mean allelic frequency of T790M, ranged from 0.17% to 40.15% across the tumors. Three main patterns of distribution were observed. In two cases, T790M was present at low level (<1% AF) prevalence throughout the entire tumor. Five cases were characterized by the presence of distinct sub-clonal region, defined as T790M AF high in one or adjacent regions surrounded by regions with low or zero T790M AF. In one case, T790M was the predominant clone with T790M AF closely matching sensitizing EGFR-mutation AF. T790M tumor burden was not associated with either tumor size or recurrence free interval.

    8eea62084ca7e541d918e823422bd82e Conclusion
    

    T790M tumor cells exist prior to TKI-therapy in a majority, if not all, EGFR-mutated lung adenocarcinoma that developed T790M mutation as the resistance mechanism to EGFR TKI therapy, rather than by de novo acquisition during TKI-therapy exposure. However, pre-treatment T790M tumor burden did not appear to be associated with recurrence free survival, although this requires more cases for confirmation.

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