Author of

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  P1.09 - Pathology (ID 173)

  • Event: WCLC 2019
  • Type: Poster Viewing in the Exhibit Hall
  • Track: Pathology
  • Presentations: 1
  • Moderators:
  • Coordinates: 9/08/2019, 09:45 - 18:00, Exhibit Hall

  • 31164

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    P1.09-03 - Clinicopathological Characteristics for NSCLC Harboring EGFR Exon 20 Insertion (ID 1211)

    09:45 - 18:00  |  Author(s): Masamichi Mineshita
    • Abstract

    Background
    

    For the majority of EGFR-mutant NSCLC patients harboring exon 19 deletion or exon 21 L858R, EGFR-TKIs are key therapies for outstanding anti-tumor effects. However, for the population harboring minor mutations, clinical benefit of EGFR-TKIs are controversial. Specifically, exon 20 insertion is acknowledged as a poor prognostic mutation type compared to other minor mutations. There are few reports describing clinicopathological characteristics harboring exon 20 insertion NCSLC.

    Method
    

    We retrospectively analyzed patients harboring EGFR exon 20 insertion at our institution over 3 years. Clinical testing for the detection of EGFR mutations was cobas® EGFR Mutation Test v2. We evaluated pathological features for diagnostic specimens or re-biopsy samples, CT or PET images for the detection of primary lesions or metastatic locations.

    Result
    

    A total of 213 EGFR-mutant adenocarcinomas were reviewed for the study and screened. Of these, 19 were positive for exon 20 insertion (8.9%). Of 19 cases, 13 displayed advanced stage while 6 cases were classified as early stage. Compound major mutation was detected in 26.3% (3 cases were exon 19 deletion; 2 cases were exon 21 L858R). In advanced cases, the location of primary lesions was found mainly in the subpleural domain (84.6%), and pleural dissemination was confirmed in 77%. The majority of cases included pleural effusion. Furthermore, 70% contained mucinous type pathologically in advanced cases. In total, more than half of the cases showed well-differentiated subtypes pathologically, which was contrary to a past report¹⁾.

    Conclusion
    

    Contrary to a past report, EGFR exon 20 insertion in adenocarcinoma often showed pathologically mucinous and well-differentiated subtypes. For clinical characteristics, especially in advanced stage, pleural dissemination and effusion were observed with high frequency, which might be due to the primary lesion often located in the subpleural domain.

    1) Mol Cancer Ther; 2012(2); 220–9