PD-L1 protein expression in relation to recurrence score values in early-stage ER + breast cancer

Purpose We assessed associations between PD-L1 protein expression, RS, tumor grade, and stromal tumor-infiltrating lymphocyte (TIL) count in early-stage ER + cancers. Methods FFPE tissue blocks of 213 patients with RS in 2012–2017 were identified. PD-L1 immunohistochemistry was performed with SP142 assay, cases with ≥ 1% tumor-infiltrating immune cell positivity in the tumor area were considered PD-L1 + . TIL scores were determined following the international TIL counting guidelines. PD-L1 expression positivity rates were compared across RS ( 25) and TIL categories ( 30%), and tumor grade using Wilcoxon and Chi-square tests. Multivariate analysis was performed using logistic regression. Results PD-L1 and TIL results were available for 201 and 203 patients. Overall, 53% of cases were PD-L1 +. PD-L1 expression was higher among cases with RS > 25, versus RS 30%, 92% were PD-L1 + versus 44% PD-L1 + among TIL 25. PD-L1 expression also correlates with TIL score.