Correlation between PD-L1 expression and clinicopathological characteristics in triple-negative breast cancer patients

Abstract

Background & objectives: While immunotherapy is emerging as an effective treatment option for advanced triple-negative breast carcinoma (TNBC) patients, the clinicopathological significance of PD-L1 expression in TNBC remains unclear. Our objective was to investigate the association between PD-L1 expression and clinicopathological characteristics in TNBC. Methods: The study group comprised 47 TNBC patients in which PD-L1 status was evaluated by immunohistochemistry with SP142 assay on the Ventana BenchMark. All PDL1(+) tumour-associated immune cells (IC) were quantified as % of the tumour area. Tumours were classified as PDL1(+)(>=1%) or PD-L1(-)(<1%). The statistical significance of the correlation between PD-L1 status and clinicopathological characteristics was determined by chi-square test. Results: PD-L1(+) were 24(51.1%) of the 47 TNBC patients whose median age at diagnosis was 59 (range, 39-79). 53.5% (23/43) of the primary and 25%(1/4) of the metastatic TNBC cases were PD-L1(+). 21(87.5%) of the PD-L1(+) TNBC had IC1( 1 and <5%), 2(8.3%) had IC2( 5 and <10%), and 1(4.2%) had IC3( 10) score. The PD-L1(+) status significantly associated with high histological grade (G3, P=0.022), and higher proliferative index (Ki-67>35%, P=0.004), while the correlation with larger tumour size (>2 cm, P=0.055) did not reach statistical significance. No significant relationship was found between PD-L1 status and other variables such as patients` age, postoperative stage, tumour status, lymph nodal status, tumour type, vascular invasion, and p53 expression. Conclusion: Our preliminary results suggest that PD-L1 expression is associated with several high-risk clinicopathological parameters in TNBC patients. Further larger studies are warranted to clarify the clinical relevance of PD-L1 expression in TNBC patients.