Fit-For-Purpose PD-L1 Biomarker Testing For Patient Selection in Immuno-Oncology: Guidelines For Clinical Laboratories From the Canadian Association of Pathologists-Association Canadienne Des Pathologistes (CAP-ACP)

Carol C. Cheung, MD, PhD, JD, Penny Barnes, MD, Gilbert Bigras, MD, PhD,§ Scott Boerner, MD, Jagdish Butany, MBBS, MS, Fiorella Calabrese, MD, Christian Couture, MD, PhD, Jean Deschenes, MD, Hala El-Zimaity, MD, PhD, Gabor Fischer, MD, PhD, Pierre O. Fiset, MD, PhD, John Garratt, RT,∥∥ Laurette Geldenhuys, MBBCH, FFPATH, MMED, FIAC, MAEd, C. Blake Gilks, MD, Marius Ilie, MD, PhD, Diana Ionescu, MD, Hyun J. Lim, PhD, Lisa Manning, BSc, Adnan Mansoor, MD, Robert Riddell, MD, Catherine Ross, MD, Sinchita Roy-Chowdhuri, MD, PhD, Alan Spatz, MD, MSc, Paul E. Swanson, MD, Victor A. Tron, MD, Ming-Sound Tsao, MD, Hangjun Wang, MD, Zhaolin Xu, MD, and Emina E. Torlakovic, MD, PhD, On behalf of the Canadian Association of Pathologists-Association Canadienne Des Pathologistes’ National Standards Committee for High Complexity Testing
(CAP-ACP NSCHCT)

Abstract: Since 2014, programmed cell death protein 1 (PD-1)/ programmed cell death ligand 1 (PD-L1) checkpoint inhibitors have been approved by various regulatory agencies for the treatment of multiple cancers including melanoma, lung cancer, urothelial carcinoma, renal cell carcinoma, head and neck can- cer, classical Hodgkin lymphoma, colorectal cancer, gastro- esophageal cancer, hepatocellular cancer, and other solid tumors. Of these approved drug/disease combinations, a subset also has regulatory agency-approved, commercially available companion/ complementary diagnostic assays that were clinically validated using data from their corresponding clinical trials. The objective of this document is to provide evidence-based guidance to assist clinical laboratories in establishing fit-for-purpose PD-L1 bio- marker assays that can accurately identify patients with specific tumor types who may respond to specific approved immuno- oncology therapies targeting the PD-1/PD-L1 checkpoint. These recommendations are issued as 38 Guideline Statements that address (i) assay development for surgical pathology and cyto- pathology specimens, (ii) reporting elements, and (iii) quality assurance (including validation/verification, internal quality as- surance, and external quality assurance). The intent of this work is to provide recommendations that are relevant to any tumor type, are universally applicable and can be implemented by any clinical immunohistochemistry laboratory performing predictive PD-L1 immunohistochemistry testing.