Technical ArticlesPD-L1 Copy Number Variation Does Not Correlate With PD-L1 Expression or Response to Anti-PD-1 Immunotherapy In Patients With Advanced MelanomasPérottet, Jérémy BM*; Le Goff, Emeline BSc*; Legoupil, Delphine MD†; Quéré, Gilles MD†; Schick, Ulrike MD, PhD†; Marcorelles, Pascale MD, PhD*; Uguen, Arnaud MD, PhD*,†Author Information *Department of Pathology, CHRU Brest †CHRU Brest, Institute of Oncology and Hematology, Brest, France J.P. and E.L.G. contributed equally. The authors declare no conflict of interest Reprints: Arnaud Uguen, MD, PhD, Department of Pathology, University Hospital Morvan, 5, Avenue Foch 29609, Brest, France (e-mail: firstname.lastname@example.org). Received June 10, 2018 Accepted September 11, 2018 Applied Immunohistochemistry & Molecular Morphology: February 2020 - Volume 28 - Issue 2 - p 161-165 doi: 10.1097/PAI.0000000000000712 Buy Metrics Abstract Predicting the response to PD-1/PD-L1 immune checkpoint blockade in patients with metastatic melanoma remains challenging. In this study, we have investigated for the relationships between PD-L1 expression, PD-L1 copy number variations, and the response to anti-PD-1 therapies. We studied the formalin-fixed paraffin-embedded tumor samples of 36 patients with metastatic melanoma using PD-L1 immunohistochemistry (IHC) and PD-L1/chromosome 9 fluorescent in situ hybridization (FISH). PD-L1 IHC was positive in 3 patients (8.33%, with >5% stained tumor cells) and PD-L1 FISH test revealed 5 (13.8%) PD-L1 amplifications, 8 (22.2%) PD-L1 gains, and 2 (5.5%) PD-L1 losses. Among 14 responders and 13 nonresponders to anti-PD-1 immunotherapy, we concluded that there was no significant relationship between PD-L1 expression, PD-L1 copy number variations, and the response to anti-PD-1 therapies. In our study, the determination of PD-L1 expression using IHC and PD-L1 copy number using FISH was insufficient to predict the response to PD-1/PD-L1 immune checkpoint blockade in patients with advanced melanomas. Copyright 2020 Wolters Kluwer Health, Inc. All rights reserved.