Predictive and prognostic value of PDL1 protein expression in breast cancer patients in neoadjuvant setting

Objective: Programmed death-ligand-1 (PDL1) is a molecule involved in immune evasion in various kinds of tumors. Here, we aim to determine whether the expression of PDL1 protein is related to the response of patients to neoadjuvant therapy and survival outcome. Methods: Immunohistochemistry (IHC) was performed on paraffin-embedded tumor samples from core needle biopsy before neoadjuvant therapy (NAT). Univariate and multivariate logistic regression were used to analyze the associations between PDL1 protein expression and pathological complete response (pCR) outcome. Kaplan-Meier plot and log-rank test were used to compare disease-free survival (DFS) between groups. A cox proportional hazards model was used to calculate the adjusted hazard ratio (HR) with 95% confidential interval (95%CI). Results: A total of 94 patients were included for IHC testing. PDL1 protein expression on tumor cells was associated with better pCR rate in both univariate (OR = 2.621, p = 0.043) and multivariate (OR = 3.595, p = 0.029) logistic regression analysis. It was also associated with shorter DFS both by log-rank test (p = 0.015) and cox hazard model (HR = 22.824, 95%CI 1.621–321.284, p = 0.020). In hormone receptor (HR)-positive patients, PDL1 protein expression was also associated with better pCR (OR = 2.362, p = 0.022). It was also associated with poor DFS (HR = 18.821, 95%CI 1.645–215.330, p = 0.018). Conclusions: Our results show that PDL1 protein expression is a predictive biomarker of pCR and a prognostic factor of DFS in breast cancer patients and HR-positive subgroups.