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  P3.09 - Pathology (Not CME Accredited Session) (ID 975)

  • Event: WCLC 2018
  • Type: Poster Viewing in the Exhibit Hall
  • Track:
  • Presentations: 1
  • Moderators:
  • Coordinates: 9/26/2018, 12:00 - 13:30, Exhibit Hall

  • 27577

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    P3.09-02 - Utilization of Laboratory Developed Tests for PD-L1 Evaluation is Dependent on Tumor Type (ID 13781)

    12:00 - 13:30  |  Presenting Author(s): Jingxin Qiu
    • Abstract
    • Slides

    Background
    

    PD-L1 expression level evaluated by immunohistochemistry plays an important role in immunotherapy for many malignancies including non-small cell carcinoma of the lung (NSCLC), adenocarcinoma of the gastroesophageal junction/stomach (GEJ-G), melanoma and etc. With the growing number of indications for the use of PD-L1 immunotherapy, it has become impracticable for laboratories to adopt and maintain the various FDA approved assays for different tumor types. Harmonization to a standard assay would alleviate the current challenges and allow testing to be uniform among laboratories. The primary objective of this study was to determine if laboratory developed tests (LDTs) utilizing available antibodies are concordant with the FDA approved assays in NSCLC, melanoma and GEJ-G, and can therefore serve as alternatives for FDA approved assays.

    a9ded1e5ce5d75814730bb4caaf49419 Method
    

    Multiple tissue microarray slides containing NSCLC (714 cases), melanoma (87 cases) and GEJ-G (194 cases) were stained for PD-L1 with the 22C3 pharmDx Kit, the 28-8 pharmDx Kit, and/or three LDTs (clones 22C3, 28-8 and E1L3N). PD-L1 expression on tumor cells was scored for NSCLC and malignant melanoma, whereas expression on tumor cells and immune cells was scored for GEJ-G. All TMA slides were digitally scanned and independently evaluated by three board certified pathologists (JQ, AC, and BB) who were blinded to staining conditions. Raw scores were converted to a composite score based on the range of raw scores. Composite scores were compared for level of agreement utilizing a Kappa score and interclass correlation coefficients displayed on Bland-Altman plots.

    4c3880bb027f159e801041b1021e88e8 Result
    

    For NSCLC, the two FDA approved assays have a high level of concordance (Kappa 0.88, 95% CI 0.85-0.90) and the two LDTs (22C3 and E1L3N) also have high level of concordance (Kappa 0.82, 95% CI 0.78-0.85); however, concordance between two FDA approved assays and the two LDTs was low. For gastric adenocarcinoma, the 22C3 FDA approved assay and 22C3 LDT has a high level of concordance (Kappa 0.90, 95% CI 0.86-0.94), but the E1L3N LDT has a low level of concordance with both the 22C3 FDA approved assay and the 22C3 LDT. For malignant melanoma, there was low concordance among two FDA approved assays and two LDTs (28-8 and E1L3N).

    8eea62084ca7e541d918e823422bd82e Conclusion
    

    These results suggest that although LDTs can be used for evaluating PD-L1 in tumor, the utilization of LDT is tumor type dependent. One single LDT may not be sufficient to serve as appropriate alternative for the FDA approved assays on different types of tumor.

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