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M. Mansour



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    P1.09 - Mesothelioma (ID 695)

    • Event: WCLC 2017
    • Type: Poster Session with Presenters Present
    • Track: Mesothelioma
    • Presentations: 1
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      P1.09-010 - PD-L1 Reactivity of Tumor Cells Can Successfully Be Determined in Malignant Mesothelioma Effusions  (ID 10008)

      09:30 - 16:00  |  Author(s): M. Mansour

      • Abstract
      • Slides

      Background:
      Malignant Mesothelioma (MM) is an aggressive, fatal tumor. Current therapeutic options only marginally improve survival. Programmed Cell Death Ligand 1 (PD-L1) is a dominant mediator of immunosuppression, binding to Programmed Cell Death 1 (PD-1). PD-L1 is up-regulated in cancer cells and the PD-1/PD-L1 pathway plays a critical role in tumor immune evasion, thus providing a target for anti-tumor therapy. Further, a correlation between PD-L1 expression and prognosis has been reported. Studies performed on histological material have revealed expression of PD-L1 in MM but no study has so far been performed on MM effusions.

      Method:
      PD-L1 expression was determined by a commercially available antibody (clone 28-8) in 74 formalin-fixed, paraffin-embedded cell blocks from body effusions obtained at diagnosis from patients with MM. The presence of MM cells was confirmed with CK5/6, Calretinin and EMA and the admixture of macrophages was assessed with CD68. Only cases containing more than 100 tumor cells were assessed. Partial or total circumferential staining in tumor cells, regardless of intensity, was considered positive. Survival time was calculated from the appearance of the first malignant effusion until death.

      Result:
      Out of 63 samples with sufficient cell block material, only 2 had to be eliminated due to few tumor cells (<100). Reactivity was seen in 23/61 (38%) of cases and was classified as ≥ 1-5% (9 cases), > 5-10% (4 cases), > 10-50% (4 cases) and > 50% (6 cases) positive cells. Survival times did not differ significantly between patients with PD-L1 positive and PD-L1 negative tumors (median 16 resp. 10 months, log rank p=0.16). Figure 1 PDL-1 reactivity in mesothelioma effusion (> 50% PD-L1 positive malignant cells) Left: HTX staining; Right: PD-L1



      Conclusion:
      MM effusions are suitable for immunocytochemical (ICC) assessment of PD-L1 expression in malignant cells and the results are similar to those reported for histological specimens

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