PD-L1 (SP142 and 22C3) immunohistochemistry in clinical metastatic triple-negative or low hormone receptor breast carcinomas: experience from a large academic institution

The discovery of new immune checkpoint molecules has led to the emergence of new treat-ments for metastatic breast carcinoma. We aimed to investigate PD-L1 (SP142 and 22C3) expression in 77 clinical metastatic triple-negative or low hormone receptor (< 10%) breast carcinomas (TNBC/ LHRBC). SP142 was positive in 23.4% of cases (18/77). SP142-positive (SP142+) cases showed lower liver metastasis and androgen receptor expression, but increased tumor-infiltrating lymphocytes than SP142-negative (SP142-) cases in univariate analysis, but only increased tumor-infiltrating lympho-cytes in multivariate analysis. 22C3 testing was available in 21 cases including 14 with combined pos-itive score (CPS) > 10 (9 SP142-and 5 SP142+) and 7 with CPS < 10 (7 SP142-). Ten (13%) patients received immunotherapy including 8 SP142+ (7 with atezolizumab and 1 with pembrolizumab) and 2 SP142-cases (2 with pembrolizumab). Survival data showed a trend of increased survival rate in SP142+ (72.2%) when compared to SP142-patients (55.9%). Our study provides unique insights into the distribution of PD-L1 staining in metastatic breast carcinomas in a real-world clinical setting.(C) 2022 Published by Elsevier Inc.