[Expression comparison and clinical significance of PD-L1 (22C3) and PD-L1 (SP142) in triple negative breast cancer]

Objective: To investigate the expression of programmed death ligand-1 (PD-L1, SP142) and PD-L1 (22C3) in triple-negative breast cancer (TNBC), and analyze their correlation with the clinicopathological factors and prognosis. Methods: The clinicopathologic data of 259 patients with TNBC treated in Cancer Hospital from August 2010 to December 2013 were collected. Whole section of surgical tissue samples were collected to conduct PD-L1 (SP142) and PD-L1 (22C3) immunohistochemical (IHC) staining. The PD-L1 expression in tumor cells and tumor infiltrating immune cells were visually assessed respectively, the relationship between PD-L1 expression and clinicopathologic characterizes were analyzed. Univariable and multivariable Cox proportional hazards regression models were used to test the correlations between PD-L1 expression and disease-free survival (DFS) and overall survival (OS). Results: The positive rates of SP142 (immune cell score, ICs≥1%) and 22C3 (combined positive score, CPS≥1) were 42.1%(109/259) and 41.3%(107/259) in TNBC tissues, respectively, with a total coincidence rate of 82.3%. The Kappa value of positive expression cases was 0.571 and the distribution difference of SP142 and 22C3 positive expression cases was statistically significant (P<0.001). The PD-L1 positive patients were less likely to have vascular invasion (P<0.05), but with higher histological grade and Ki-67 proliferation index (P<0.05). The recurrence/metastasis cases(8) of the patients with positive PD-L1 (SP142) was significantly lower than that of patients with negative PD-L1(SP142, 27, P=0.016). The positive expression of PD-L1 (SP142) patients were longer DFS (P=0.019). The OS of patients with positive PD-L1 (SP142) were longer than those with negative PD-L1 (SP142), but without significance (P=0.116). The positive expression of PD-L1 (22C3) was marginally associated with DFS and OS of patients (P>0.05). Conclusions: The expression of PD-L1 (22C3) is different from that of PD-L1 (SP142) in TNBC, and the two antibodies can't be interchangeable for each other in clinical tests. PD-L1 (SP142) status is an independent prognostic factor of DFS in TNBC. The DFS is significantly prolonged in patients with positive expression of PD-L1 (SP142).