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Original research
Multicentre study on the consistency of PD-L1 immunohistochemistry as predictive test for immunotherapy in non-small cell lung cancer
  1. Rogier Butter1,
  2. Nils A 't Hart2,
  3. Gerrit K J Hooijer1,
  4. Kim Monkhorst3,
  5. Ernst-Jan Speel4,
  6. Paul Theunissen5,
  7. Erik Thunnissen6,
  8. Jan H Von der Thüsen7,
  9. Wim Timens2,
  10. Marc J van de Vijver1,8
  1. 1 Department of Pathology, Cancer Center Amsterdam, Amsterdam University Medical Centers, University of Amsterdam, Amsterdam, The Netherlands
  2. 2 Department of Pathology and Medical Biology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
  3. 3 Department of Pathology, The Netherlands Cancer Institute, Antoni van Leeuwenhoek Hospital, Amsterdam, The Netherlands
  4. 4 Department of Pathology, GROW-School for Oncology and Developmental Biology, Maastricht University Medical Center, Maastricht, The Netherlands
  5. 5 Department of Pathology, Zuyderland Medical Center, Heerlen, The Netherlands
  6. 6 Department of Pathology, Amsterdam University Medical Centers, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
  7. 7 Department of Pathology, Erasmus University Medical Center, Erasmus University Rotterdam, Rotterdam, The Netherlands
  8. 8 Department of Pathology, Cancer Center Amsterdam, Amsterdam University Medical Centers, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
  1. Correspondence to Rogier Butter, Department of Pathology, Cancer Center Amsterdam, Amsterdam University Medical Centers, University of Amsterdam, Amsterdam, 1105 AZ, The Netherlands; r.butter{at}amc.uva.nl

Abstract

Aims Investigate the impact of interlaboratory- and interobserver variability of immunohistochemistry on the assessment of programmed death ligand 1 (PD-L1) in non-small cell lung cancer (NSCLC).

Methods Two tissue microarrays (TMAs) were constructed from 50 (TMA-A) and 51 (TMA-B) resected NSCLC cases, and distributed among eight centres. Immunostaining for PD-L1 was performed using Agilent’s 22C3 pharmDx Assay (pharmDx) and/or a 22C3 laboratory developed test (LDT). The interlaboratory variability of staining- and interobserver variability of scoring for PD-L1 were assessed in selected critical samples (samples at the cut-off of positivity) and non-critical samples. Also, PD-L1 epitope deterioration in time in stored unstained slides was analysed. Krippendorff’s alpha values (0=maximal, 1=no variability) were calculated as measure for variability.

Results For interlaboratory variability of immunostaining, the percentage of PD-L1 positive cases among centres ranged 40%–51% (1% cut-off) and 23%–30% (50% cut-off). Alpha values at 1% cut-off were 0.88 (pharmDx) and 0.87 (LDT) and at 50% cut-off 0.82 (pharmDx) and 0.95 (LDT). Interobserver variability of scoring resulted in PD-L1 positive cases ranging 29%–55% (1% cut-off) and 14%–30% (50% cut-off) among pathologists. Alpha values were at 1% cut-off 0.83 (TMA-A) and 0.66 (TMA-B), and at 50% cut-off 0.77 (TMA-A) and 0.78 (TMA-B). Interlaboratory variability of staining was higher (p<0.001) in critical samples than in non-critical samples at 50% cut-off. Furthermore, PD-L1 epitope deterioration in unstained slides was observed after 12 weeks.

Conclusions The results provide insight in factors contributing to variability of immunohistochemical assessment of PD-L1, and contribute to more reliable predictive testing for PD-L1.

  • lung cancer
  • immunohistochemistry
  • oncology
  • pulmonary pathology
  • histopathology

https://doi.org/10.1136/jclinpath-2019-205993

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    Footnotes

    • Handling editor Cheok Soon Lee.

    • Contributors Conception or design of the work: all authors. Data collection: all authors. Data analysis and interpretation: RB, GKJH and N‘tH. Drafting the article: RB and MJvdV. Critical revision of the article: all authors. Final approval of the version to be published: all authors.

    • Funding This study was funded by Merck Sharp and Dohme Corp., a subsidiary of Merck & Co., Inc., Kenilworth, NJ, USA.

    • Competing interests RB: none. N‘tH: MSD (unrestricted grant), Pfizer (personal fee). KM: Roche (research grant, personal fee), MSD (research grant, personal fee), Astra Zeneca (research grant, personal fee), Pfizer (personal fee), Benecke (personal fee), BMS (personal fee), Abbvie (personal fee), Diaceutics (personal fee). E-JS: MSD (research grant, personal fee), BMS (research grant, personal fee), Novartis (research grant), AstraZeneca (research grant), AbbVie (personal fee), Bayer (personal fee), Roche (personal fee). ET: HistoGeneX (personal fee), Roche Diagnostics (personal fee). JHVdT: Astellas (research grant), BMS (research grant, personal fee), AbbVie (personal fee), Astra Zeneca (personal fee), Boehringer-Ingelheim (personal fee), BMS (personal fee), Eli Lilly (personal fee), MSD (personal fee), Pfizer (personal fee), Roche (personal fee). WT: MSD (personal fee), Roche-Ventana (personal fee), Pfizer (personal fee), Astra Zeneca (personal fee), GSK (personal fee), Chiesi (personal fee), Dutch Asthma Fund (research grant), Biotest (personal fee), Novartis (personal fee), Lilly Oncology (personal fee), Boehringer Ingelheim (personal fee). MJvdV: MSD (research grant), Roche (personal fee).

    • Patient consent for publication Not required.

    • Provenance and peer review Not commissioned; externally peer reviewed.

    • Data availability statement Data are available upon reasonable request.