Harmonization of PD-L1 testing in oncology: a Canadian pathology perspective

  • D.N. Ionescu University of British Columbia
  • M.R. Downes Sunnybrook Health Sciences Centre; University of Toronto
  • A. Christofides impact Medicom Inc.
  • M.S. Tsao University of Toronto; University Health Network, Princess Margaret Cancer Centre
Keywords: Immunotherapy, lung cancer, bladder cancer, PD-L1 assays, immunohistochemistry

Abstract

Checkpoint inhibitors targeting the programmed cell death 1 protein (PD-1) and programmed cell death ligand 1 (PD-L1) are demonstrating promising efficacy and appear to be well tolerated in a number of tumour types. In non-small-cell lung cancer, head-and-neck squamous cell carcinoma, and urothelial carcinoma, outcomes appear particularly favourable in patients with high PD-L1 expression. However, assays for PD-L1 have been developed for individual agents, and they use different antibody clones, immunohistochemistry staining protocols, scoring algorithms, and cut-offs. Given that laboratories are unlikely to use multiple testing platforms, use of one PD-L1 assay in conjunction with a specific therapy will become impractical and could compromise treatment options. Methods to harmonize testing methods are therefore crucial to ensuring appropriate treatment selection. This paper focuses on lung, bladder, and head-and-neck cancer. It reviews and compares available PD-L1 testing methodologies, summarizes the literature about comparability studies to date, discusses future directions in personalized diagnostics, and provides a pathologist’s perspective on PD-L1 testing in the Canadian laboratory setting.

Author Biographies

D.N. Ionescu, University of British Columbia
Department of Pathology and Laboratory Medicine
M.R. Downes, Sunnybrook Health Sciences Centre; University of Toronto
Anatomic Pathology; Department of Laboratory Medicine and Pathobiology
M.S. Tsao, University of Toronto; University Health Network, Princess Margaret Cancer Centre
Department of Laboratory Medicine and Pathobiology; Department of Pathology
Published
2018-06-27
How to Cite
Ionescu, D., Downes, M., Christofides, A., & Tsao, M. (2018). Harmonization of PD-L1 testing in oncology: a Canadian pathology perspective. Current Oncology, 25(3), e209-e216. https://doi.org/10.3747/co.25.4031
Section
Review Article