PD-L1 Acts as a Promising Immune Marker to Predict the Response to Neoadjuvant Chemotherapy in Breast Cancer Patients

This research analyzed the clinical value of programmed death ligand 1 positivity in predicting the outcome of patients with breast cancer. The databases were searched for all eligible studies, and the data were analyzed by Stata software. We concluded that programmed death ligand 1 positivity was a promising biomarker to predict neoadjuvant chemotherapy response, but it cannot indicate the higher death or recurrence/metastasis risk. Background: Programmed death ligand 1 (PD-L1) is a negative immune stimulatory molecule that plays a key role in tumor immune escape. We analyzed the clinical value of PD-L1-positive expression in predicting the outcome of breast cancer patients and to establish its role as new biomarker to guide precise treatment. Patients and Methods: PubMed and Embase were searched for all original English-language articles published before January 30, 2019; all articles reported the predictive and prognostic implications of PD-L1(+) in breast cancer. Data were analyzed by Stata SE 12 software. Results: The PD-L1(+) rate varied from 19.7% to 77.6% in breast cancer patients. Specifically, patients with estrogen receptor-positive, progesterone receptor-positive, luminal A, luminal B, and HER2(+) disease subtypes had lower PD-L1 expression, while the PD-L1(+) percentages did not follow any trend in patients with Ki-67(+), normal-like, HER2 overexpression, and basal-like subtype. In addition, PD-L1(+) was observed to be associated with significantly improved pathologic complete response to neoadjuvant chemotherapy (odds ratio = 2.01; 95% confidence interval, 1.35-3.01; P < .05). Using PD-L1(+) to predict pathologic response showed obvious accuracy. However, PD-L1(+) did not show significant association with risk of higher recurrence or metastasis, or higher death risk (hazard ratio = 0.91, P = .655; hazard ratio = 1.00, P = .995). Conclusion: PD-L1(+) is a promising immune parameter with the potential to predict response to neoadjuvant chemotherapy, but it cannot indicate a higher risk of death, recurrence, or metastasis.