Author of

• 25946

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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

  • 27057

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    P2.09-05 - Evaluation of PD-L1-Stained Tumor Cells via the 22C3 and SP-142 Antibodies in Cohort of Patients Treated on KEYNOTE-001 (ID 12976)

    16:45 - 18:00  |  Author(s): Tristan Grogan
    • Abstract

    Background
    

    Four PD-L1 antibodies have been utilized in NSCLC clinical trials, with an analytical comparison demonstrating a high level of concordance between the percentage of PD-L1–stained tumor cells with three of these antibodies (22C3, 22C3, 28-8, and SP263), but not a fourth, SP-142 (Hirsch et al, JTO 2017). This finding led us to evaluate the relationship between the percentage of PD-L1–stained tumor cells with 22C3 and SP-142, as well as the association between the PD-L1 levels identified by each antibody and clinical outcomes in 28 NSCLC patients treated on KEYNOTE-001.

    a9ded1e5ce5d75814730bb4caaf49419 Method
    

    We performed a retrospective analysis of 28 NSCLC patients treated with pembrolizumab on the KEYNOTE-001 trial at UCLA (23pts) or MSKCC (5pts) with data cut-off 12/2017. Patients had PD-L1–stained tumor cell levels assessed by both the 22C3 antibody (Dako), via central evaluation as previously described (Garon et al, NEJM 2015) and the SP-142 antibody (Spring Bioscience) at UCLA in accordance with established methods (Zaretsky et al, NEJM 2016). Survival curves for PFS and OS were estimated using the Kaplan-Meier method and formally compared between groups using the log-rank test. The association between PD-L1–stained tumor cell levels identified by the two antibodies was assessed using the Pearson correlation coefficient.

    4c3880bb027f159e801041b1021e88e8 Result
    

    In 61% (17/28) of patients, PD-L1 levels were grouped similarly (either <1%, 1-49%, or >50%) by both antibodies. Specifically, compared to 22C3 staining, SP-142 led to the same grouping for 63% (5/8) pts with >50% staining, 85% (11/13) pts with 1-49% staining, and 14% (1/7) pts w <1% staining. Evaluating the relationship between PD-L1 grouping and clinical outcomes via the SP-142 antibody revealed improved PFS and OS in pts with higher PD-L1 expression levels, while the 22C3 antibody predicted for improved PFS in these patients, but not improved OS [SP142 (PFS,OS): (p=0.0039, p=0.0425)][22C3 (PFS,OS): p=0.0121, p=0.1222). The PD-L1 results from the SP-142 and 22C3 antibodies were strongly associated (r =0.58, p=0.001).

    8eea62084ca7e541d918e823422bd82e Conclusion
    

    The PD-L1–stained tumor cell levels in the majority of patients evaluated were similarly grouped into one of three categories (<1%, 1-49%, or >50%) by both 22C3 and SP142. This analysis is limited by small patient number, but suggests that the number of PD-L1–stained tumor cells identified by each antibody is similar and a higher PD-L1 level identified by either antibody predicts for improved clinical outcomes with pembrolizumab.

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