Author of

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  P26 - Mesothelioma, Thymoma and Other Thoracic Malignancies - Thymic Malignancies (ID 218)

  • Event: WCLC 2020
  • Type: Posters
  • Track: Mesothelioma, Thymoma and Other Thoracic Malignancies
  • Presentations: 1
  • Moderators:
  • Coordinates: 1/28/2021, 00:00 - 00:00, ePoster Hall

  • 35981

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    P26.10 - Molecular Characterization of Patients with Thymoma and Thymic Carcinoma (ID 1495)

    00:00 - 00:00  |  Presenting Author(s): Xun Yang
    • Abstract
    • Slides

    Introduction
    

    Thymoma and thymic carcinoma are rare intrathoracic tumors that account for approximately 0.2% to 1.5% of all malignancies. Distinct clinical features were reported for thymoma and thymic carcinoma in the previous studies. This study aimed to explore the molecular profiling of thymoma and thymic carcinoma by multi-gene sequencing.

    Methods
    

    Formalin-fixed tumor samples from patients with thymoma or thymic carcinoma were collected for next-generation sequencing (NGS) with a panel of more than 381 genes in 3DMed laboratory from January, 2017 to March, 2020. Somatic mutations including single nucleotide variants, copy number variations, fusion and rearrangements, and germline mutations were detected. PD-L1 expression was assessed in tumor samples with the use of the commercially available PD-L1 IHC 22C3 pharmDx assay (Agilent Technologies, Carpinteria, CA, USA) or Ventana PD-L1 SP263 assay (Ventana Medical Systems, Tucson, AZ, USA).

    Results
    

    There are 51 patients with thymoma (n=30) or thymic carcinoma (n=21) being included for the analysis. In overall, 56.9% (29/51) are female and 43.1% (22/51) are male patients. The median age of the total population is 49 (IQR range, 38.75-62), and 31.4% (16/51) of the patients were no older than 40 years old. No significant differences were observed for the distribution of sex or age between patients with thymoma and thymic carcinoma (p>0.5). Pathogenic or very likely pathogenic somatic mutations were detected in 66.7% (34/51) of the patients, including 29.4% (15/51) with frameshift mutations. A significantly lower rate of pathogenic somatic mutations were found in thymoma patients (46.7%, 14/30) versus thymic carcinoma patients (95.2%, 20/21) (p=0.0002). In overall, limited druggable oncogenic mutations were found in the studied cohort. The most frequently mutated genes are highly varied between these two groups, including TP53 (13.3%) and CYLD (10.0%) in thymoma, and CDKN2A (28.6%), CDKN2B (19.0%), TET2 (14.3%), and TNFAIP3 (14.3%) in thymic carcinoma. Among the patients evaluable for microsatellite stability status (n=48), only one 62-year-old male with TGFBR2 mutation exhibited microsatellite instability-high status (MSI-H). In addition, PD-L1 expression testing was performed in 44 patients including 25 with thymoma and 19 with thymic carcinoma. A larger proportion of patients with positive PD-L1 expression was observed in thymoma compared to thymic carcinoma (PD-L1≥1%, 88.0% vs 63.2%, p=0.074; PD-L1≥50%, 64.0% vs 36.8%, p=0.13), though not reaching statistical significance.

    Conclusion
    

    Our study have provide more evidences for the molecular features of patients with thymoma and thymic carcinoma, which may shed lights on the future treatment in cancer patients.

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