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X. Cao



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    OA 13 - Immuno-Biology (ID 677)

    • Event: WCLC 2017
    • Type: Oral
    • Track: Immunology and Immunotherapy
    • Presentations: 1
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      OA 13.02 - Distribution of PD-L1 Tumor Expression by Assay Type in Patients with Metastatic NSCLC (MNSCLC) (ID 9679)

      11:10 - 11:20  |  Author(s): X. Cao

      • Abstract
      • Presentation
      • Slides

      Background:
      Pembrolizumab was initially approved as a single agent by the US FDA on October 2, 2015, for treating patients with mNSCLC who have disease progression on or after platinum-containing chemotherapy and PD-L1 tumor expression ≥50%, as determined by the FDA-approved test (Dako 22C3). Subsequent approvals for first-line therapy and expanded second-line therapy followed in October 2016. Our aim was to study PD-L1 testing patterns in US oncology practices from October 2015 through March 2017 and the potential impact of the PD-L1 IHC assay type on measurement of PD-L1 tumor expression.

      Method:
      This retrospective, observational study drew on de-identified, longitudinal data from a large electronic medical record database (Flatiron Health) representing 17% of incident oncology cases in the US. Eligible patients were adults (≥18 years) with histologically/cytologically confirmed initial diagnosis of mNSCLC (stage IV) or metastatic recurrence from October 2015 through March 2017. We determined the rate of PD-L1 testing (test date defined as the result date) and distribution of PD-L1 tumor expression (percentage of tumor cells staining for PD-L1) by IHC assay type.

      Result:
      The 7879 eligible patients included 4111/3768 (52%/48%) men/women; 5123 (65%) were >65 years old, and 6706 (85%) had a history of smoking. The rate of PD-L1 testing increased consistently over time from 15% in Q4/2015 to 70% in Q1/2017. Of 1728 patients with mNSCLC tested for PD-L1, 77%, 5%, 4%, and 19% were tested using Dako 22C3, Dako 28-8, Ventana SP142, and laboratory-developed tests (LDTs), respectively. Measured PD-L1 expression varied significantly (χ[2] p<0.0001) across the four assay types, although there was no significant difference (p=0.053) among the remaining three assays when the SP142 assay was excluded (Table).Figure 1



      Conclusion:
      We found no significant differences in measuring PD-L1 tumor expression using Dako 22C3, Dako 28-8, and LDTs; however, results of the SP142 assay appeared discordant.

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