The Prognostic Value of PD-L1 Expression in Triple-Negative Breast Cancer: A Cohort Study and Systematic Literature Review.
The programmed death (PD)-1 protein has potent inhibitory effects on T-lymphocytes and other immune cells, including B-lymphocytes and monocytes. PD-L1 may also be expressed by tumor cells to evade immune killing, thereby increasing tumorigenesis and invasiveness.
Accordingly, PD-L1 has been associated with poor prognosis in non-small cell lung carcinoma, melanoma, renal cell carcinoma, and esophageal/gastric carcinoma. Overall, PD-L1 is expressed by a minority of human breast tumors, and there are conflicting reports regarding the prognostic import of PD-L1 in breast cancer: some studies have associated overexpression of PD-L1 with inferior overall survival, while other studies showed improved prognosis.
A recent meta analysis of PD-L1 expression in breast cancer concluded that expression of PD-L1 is associated with lymph node positivity, higher histologic grade, hormonal receptor-negative status, and shorter overall survival.
However, there is still a lack of consensus regarding the prognostic value of PD-L1 in triple-negative breast cancers. Because TNBC represent 10-20% of new diagnoses of breast cancer, have inferior
clinical outcomes, and lack molecularly targeted therapies, there is intense interest in emerging immunotherapeutic approaches such as agents that target PD-L1.
To better understand the prevalence of PD-L1 positivity and its association with survival in TNBC, we undertook a retrospective cohort study at a major academic medical center and a systematic review of comparable studies.
All samples were tissue from breast tumors that had been excised,
processed into formalin-fixed, paraffin-embedded blocks, and subjected to routine pathologic examination. The latter examination had included immunohistochemistry and fluorescent in situ
hybridization to determine endoplasmic reticulum, per rectum, and HER2/neu status.
Pathol Lab Med Open J. 2019; 1(1): 37-44. doi: 10.17140/PLMOJ-1-107