Author of

• 34656

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  P33 - Pathology - Immunotherapy Biomarker (ID 101)

  • Event: WCLC 2020
  • Type: Posters
  • Track: Pathology, Molecular Pathology and Diagnostic Biomarkers
  • Presentations: 1
  • Moderators:
  • Coordinates: 1/28/2021, 00:00 - 00:00, ePoster Hall

  • 34660

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    P33.02 - Comparison of PD-L1 Protein Expression Between Primary and Metastatic Lesions in Lung Cancer Patients (ID 3550)

    00:00 - 00:00  |  Presenting Author(s): Myrto Moutafi
    • Abstract
    • Slides

    Introduction
    

    PD-L1 expression assessed by IHC is the central companion diagnostic test for immunotherapy. However, most trials have not stipulated the tissue source used to assess expression. Here we assess PD-L1 expression as performed in the “real world” to determine if sampling sites, histologic subtypes, genders and age groups affect the likelihood of high-level expression.

    Methods
    

    A retrospective data analysis of the FMI clinical database was conducted on lung cancer cases that were assessed for PD-L1 expression in the context of routine care. All samples were stained with the DAKO 22C3 CDx assay at Foundation Medicine, Inc. (FMI) North Carolina laboratory. PD-L1 expression was evaluated and scored with the Tumor Proportional Score (TPS) methodology; TPS = Number of PD-L1 positive tumor cells / (Total number of PD-L1 positive + PD-L1 negative tumor cells) * 100%. In all tests, two-sided P-values of less than 0.05 were considered significant. Statistical analysis was conducted using Prism 8 software and RStudio version 4.0.1.

    Results
    

    15,028 samples from 7599 male and 7429 female lung cancer patients, were analyzed. Metastatic lesions were more likely to be PD-L1 high (TPS ≥ 50%) compared with primary lesions (33.8%) vs (28.4%) ;(Odds Ratio [OR] 1.28, 95% Confidence Interval [CI] 1.19-1.37; P<.001). This observation was seen in samples from lymph nodes (OR 1.58,95% CI 1.43-1.74; P<.001), pleural fluid (OR 1.48, 95% CI 1.23-1.78;P<.001), soft tissue (OR 1.3, 95% CI 1.08-1.58;P=.007) and adrenal gland (OR 1.7, 95%CI 1.3-2.22; P<.001) but not with those from liver (OR 0.98, 95% CI 0.83-1.16; P=.835), brain (OR 1.00, 95%CI 0.85-1.18; P=.994) and bone (OR 0.83, 95%CI 0.67-1.04; P=.101)​. Metastatic lesions of patients with non-squamous histology were more likely to have TPS ≥ 50% in comparison with primary tumors (OR 1.37, 95% CI 1.27-1.49; P<.001) but this was not the case for patients with squamous histology (OR 0.83, 95% CI 0.74-1.07; P=.208). Female patients had significantly increased rates of high PD-L1 TPS compared to male patients (OR 1.08, 95% CI 1.01-1.16; P<.027); but this was driven by the higher TPS of lung squamous cell carcinoma female patients (OR 1.24, 95%CI 1.05-1.47; P=.012).

    Conclusion
    

    This study demonstrates that PD-L1 expression is associated with the sampling site, histologic type, and gender. Understanding PD-L1 expression distributions may affect trial design and patient care.

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