PD-L1 and intratumoral immune response in breast cancer
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Zhi-Qiang Wang1,4, Katy Milne1, Heather Derocher1,2, John R. Webb1,2, Brad H. Nelson1,2,3 and Peter H. Watson1,4
1Trev & Joyce Deeley Research Centre, British Columbia Cancer Agency, Victoria, British Columbia, Canada
2Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia, Canada
3Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada
4Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, British Columbia, Canada
Peter H. Watson, email: email@example.com
Keywords: PD-L1, CD4, CD8, CD68, breast cancer
Received: March 19, 2017 Accepted: April 28, 2017 Published: May 30, 2017
Purpose: PD-L1 is thought to play an important role in the antitumor immune response. In this study, we investigated the expression of PD-L1 within breast tumor subsets to better define its prognostic significance.
Methods: Immunohistochemistry was performed to determine PD-L1 tumor cell expression and to enumerate CD8, CD4 and CD68 tumor-infiltrating leucocytes (TIL) in a cohort of 443 breast cancers categorized by molecular subtype.
Results: Across the entire cohort, PD-L1 tumor cell expression was observed in 73/443 (16.5%) cases and associated with known indicators of poor prognosis, including low patient age, high tumor grade, ER/PR negative status, but not with outcome. However, in the Triple Negative breast cancer subset PD-L1 was associated with better recurrence free survival (RFS) especially within the Basal-like subset (Hazard ratio = 0.39, 95% CI = 0.22 - 0.86, p = 0.018). Combined PD-L1/epithelial CD8 positive status was also strongly associated with better RFS and OS (Hazard ratio = 0.12, 95% CI = 0.10 - 0.71, p = 0.010 and Hazard ratio = 0.11, 95% CI = 0.11 - 0.68, p = 0.006 respectively) in the Basal-like subgroup.
Conclusions: PD-L1 expression is associated with better patient survival in Basal-like breast cancer.
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