Programmed death-ligand 1 expression in triple negative breast cancer

Abstract

Background & Objectives: Triple negative breast cancer (TNBC) account for 10-20% of all breast subtypes and are associated with poor prognosis. There is no approved targeted therapy for these patients, yet. Programmed death-ligand 1 (PD-L1) expression has been identified in different cancers achieving good results with immunotherapy. There is limited data reporting the PD-L1 expression in TNBC. The aim of this study is to evaluate the expression of PD‑L1 in TNBC patients and to analyse the relationship between PD‑L1 expression and clinicopathological features of the patients. Methods: Paraffin tissue blocks from 19 TNBC patients were used. PD-L1 immunohistochemistry was performed using monoclonal mouse anti-PD-L1, Clone 22C3. Expression of PD-L1 was correlated with clinicopathological features. Tumours were defined as PD-L1 positive if there was membranous expression in ≥ 1% of tumour cells. Results: Median age at diagnosis was 56 (range 33-74). PD-L1 was expressed in 7 (36, 8%) of the patients. Six of the patients showed low PD-L1 expression (3-20%) and only one patient showed high expression (>50%). The PD-L1 expression showed no significant correlation with clinicopathological parameters. Although statistically not significant (p>0,05), PD-L1 was more often expressed in high grade tumours with larger size, high clinical stage and mutated p53. Conclusion: Expression of PD-L1 was found in more than one third of TNBC and correlated with poor prognostic factors. PD‑L1 may be a significant marker for predicting prognosis of TNBC patients. These data need to be confirmed in larger study group.