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Hyang Mi Ko



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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
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      P3.09-26 - Concordance of Surgical Resections and Fine Needle Biopsy-Derived Cell Block Sections for PD-L1 22C3 Immunohistochemistry   (ID 13499)

      12:00 - 13:30  |  Author(s): Hyang Mi Ko

      • Abstract
      • Slides

      Background

      A significant proportion of lung cancer patients presents at an advanced disease stage. Diagnosis and treatment in these patients is frequently based on small tissue samples such as fine needle biopsies. Eligibility for pembrolizumab immunotherapy requires assessment of the PD-L1 expression. Data on the concordance of PD-L1 assessment by immunohistochemistry between quantitatively limited samples, in particular cytology specimens, and resections are scant. We studied PD-L1 in formalin-fixed paraffin-embedded (FFPE) cell block sections of CT-guided transthoracic fine needle biopsies in comparison with the subsequent resection specimens of the primary lung tumors.

      a9ded1e5ce5d75814730bb4caaf49419 Method

      Paired specimens of fine needle biopsy-derived cell blocks and subsequent lung tumor resections of the same anatomic site were obtained from the archives of the Department of Pathology, University Health Network. Cell blocks were produced from normal saline needle rinse fluids fixed with a final concentration of 10% neutral-buffered formalin and processed using the Histogel method for paraffin-embedding. Cytology samples treated with alcohol-based fixatives were not included. Cell block sections were reviewed for a minimum of 100 tumor cells. Cases below the cellularity threshold were excluded. Staining was performed using the 22C3 pharmDxTM assay (Agilent). All cell block and representative tumor sections were assessed by three observers (1 expert pulmonary pathologist, 2 cytopathologists). Tumor proportion scores (TPS) were recorded and a final TPS was determined using the mean between expert and second closest observer. Cases close to the ≥50% cut-off underwent multiheader microscope review. Pearson, intraclass correlation coefficients and test parameters were calculated using standard statistical methods.

      4c3880bb027f159e801041b1021e88e8 Result

      43 paired cases were informative. Mean interval between biopsy and resection was 1.5 months (range 0-4). TPS of cell blocks and resections showed positive correlation (Pearson: 0.8; range 0.78 - 0.84 for individual observers). Intraclass correlation coefficients were 0.97 (cell blocks) and 0.92 (resections). 10/43 (23%) cell blocks and 9 (21%) resections were positive at TPS≥50%. 21/43 (49%) cell blocks and 19 (44%) resections were positive at TPS≥1%. Sensitivity, Specificity, PPV, NPP and accuracy were 78/74, 91/71, 70/67, 94/77 and 88/72% for the ≥50/≥1% cut-off, respectively.

      8eea62084ca7e541d918e823422bd82e Conclusion

      Cytology FFPE cell block sections showed strong positive correlation with resection specimens of the same anatomic site for PD-L1 assessment using the 22C3 pharmDxTM immunohistochemistry assay. Reliability between observers was excellent. Test parameters, in particular for the ≥50% cut-off value, were deemed acceptable for clinical use. Selected slide review of cases with discordant scores indicated tumor heterogeneity as cause.

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