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  P2.09 - Pathology (Not CME Accredited Session) (ID 958)

  • Event: WCLC 2018
  • Type: Poster Viewing in the Exhibit Hall
  • Track:
  • Presentations: 1
  • Moderators:
  • Coordinates: 9/25/2018, 16:45 - 18:00, Exhibit Hall

  • 27054

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    P2.09-02 - Comprehensive Assessment of PD-L1 Immunohistochemistry on Paired Tissue and Cytology Specimens in Non-Small Cell Lung Cancer   (ID 13248)

    16:45 - 18:00  |  Author(s): David Joubert
    • Abstract
    • Slides

    Background
    

    Molecules targeting Programmed Death Receptor 1 (PD-1) and its ligand (PD-L1) are now part of the therapeutic arsenal for patients presenting with advanced stage non-small cell lung carcinoma (NSCLC). PD-L1 staining assessed by immunohistochemistry (IHC) is currently used as a predictive biomarker to select patients likely to respond to PD-1/PD-L1 inhibitors. Despite recent data, it is still not clear if cytology specimens provide reliable and valid PD-L1 results, when compared to tissue specimens. In this project, we aimed to compare PD-L1 IHC results on tissue (biopsy and surgery) and cytology specimens from the same patient. We also wanted to assess the performance of two IHC kits as well as the intra and interobserver agreement in evaluating cytology specimens.

    a9ded1e5ce5d75814730bb4caaf49419 Method
    

    A retrospective cohort comprising 46 patients with a diagnosis of NSCLC was selected. Each patient had a surgical specimen with a corresponding cytology sample (cell block), including 20 pleural effusions, and/or a biopsy, for a total of 182 specimens. IHC was performed using 28-8 and SP263 PD-L1 kits. PD-L1 staining was measured as the percentage of tumor cells with membranous staining (tumor proportion score, TPS) as rated blindly by four evaluators. Sixty slides were then blindly reevaluated for documenting intraobserver agreement. PD-L1 TPS was grouped as <1%, 1-49% and >50%. Fleiss and Cohen’s kappas were used to evaluate TPS concordance between tissue and cytology specimens and to assess the inter and intraobserver agreement.

    4c3880bb027f159e801041b1021e88e8 Result
    

    Respectively for 28-8 and SP263 kits, 37.5 and 25.0% of the 32 patients with a cytology sample had a PD-L1 TPS of >50% with a good agreement between the kits (k=0.73, CI95% 0.50-0.97). The agreement between the cytology and surgical specimen was good (28-8: k=0.76, CI95% 0.46-1.0, SP263: k=0.75, CI95% 0.42-1.0) and was slightly lower between the 26 patients with a biopsy and a cytology specimen (28-8: k=0.71, CI95% 0.31-1.0, SP263: k=0.67, CI95% 0.19-1.0). For the evaluation of PD-L1 TPS in cytology specimens, the interobserver agreement was good (28-8: k=0.71, CI95% 0.60-0.82, SP263: k=0.63, CI95% 0.52-0.74) and the intraobserver agreement was excellent (k=0.93, CI95% 0.85-1.0).

    8eea62084ca7e541d918e823422bd82e Conclusion
    

    We showed that PD-L1 TPS evaluated in cytology samples have a good concordance with biopsy and surgical specimens. We also demonstrated that the evaluation in cytology specimen is feasible as the inter and intraobserver agreement was good to excellent. Overall, our results support the use of PD-L1 IHC on cytology specimens, however, this will need to be correlated with the clinical response to immunotherapy.

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