The Expression of PD-L1 in Different Molecular Subtypes of Triple-Negative Breast Cancer and Its Correlation with Prognosis

Objective: To investigate the expression of PD-L1 in different subtypes of triple-negative breast cancer and its correlation with the prognosis of patients. Methods: A total of 240 patients with triple-negative breast cancer (TNBC) who had not received neoadjuvant therapy before radical resection were selected for immunohistochemical study of PD-L1 expression, including 60 patients with four subtypes of TNBC. Kaplan-Meier and univariate Cox proportional hazard model analysis were used to compare the relationship between PD-L1 expression and survival time of patients with different subtypes. Results: The median follow-up time was 55.75 months (range: 23.28~120.02 months). Overall survival (OS) was significantly increased in PD-L1-positive TNBC patients compared with PD-L1-negative TNBC patients (P = 0.029). Among the different types of TNBC tissues, the highest expression rate of PD-L1 was 26.7% in immunomodulatory type (IM), which was accompanied by a better prognosis. There were significant differences in the positive expression rate of PD-L1 among different types of TNBC with different TNM stages, histological grades, and lymph node metastasis (P < 0.05), and OS was significantly prolonged in the four sub-types of TNBC patients with IM. Univariate Cox proportional model analysis showed that PD-L1 was an independent prognostic factor for TNBC. Conclusion: PD-L1 has different effects on prognosis in different types of TNBC, and the relationship between PD-L1 and prognosis is most close in IM type.