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.
Keywords: Disease-free survival; Pathologic response; Prognostic value; Programmed death ligand 1; Survival time.
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