A wide range of variables are associated with poor long-term outcomes of radical treatment in patients with prostate cancer (PCa). Expression of the programmed death-1 ligand 1 (PD-L1) in tumor might be a potential novel marker for PCa.
Aim: to evaluate the influence of PD-L1 expression status in tumor cells on long-term results of radical treatment in patients with PCa.
Materials and methods: a total of 45 patients with pathologically-proven PCa who undergone radical treatment and followed at N.N. Blokhin National Medical Research Center of Oncology were retrospectively analyzed. In all cases PD-L1 expression in tumor cells was evaluated by immunohistochemical studies of paraffin block sections obtained under direct control of pathologist. Positive expression of PD-L1(+) was defined as expression level in tumor cells ≥ 1%, while hyperexpression was diagnosed when expression level L1 ≥ 5%.
Results: PD-L1 expression and hyperexpression in tumor cells were identified in 8 (17.8%) and 6 (13.3%) cases. Median metastasis-free survival in patients with positive PD-L1 expression was 48.918 months (95% CI 42.523-55.313) and was less than in patients with negative PD-L1 expression (68.033 months, 95% CI 48.242- 87.824, p=0.090). Cancer-specific survival in patients with negative PD-L1 expression was significantly longer compared to patients with positive expression (p=0.05) and hyperexpression (p=0.024) of PD-L1 in tumor cells. Multivariate Cox analysis confirmed independent predictive value of positive expression and hyperexpression of PD-L1 in tumor cells for metastasis-free survival (HR 3.461, 95% CI 1.171-10.228, p=0.025, and HR 3.916, 95% CI 1.129-13.591, p=0.032) and cancer-specific survival (HR 7.65, 95% CI 0.69-84.51, p=0.097, and HR 9.73, 95% CI 0.87-108.78, p=0.065).
Conclusion: According to our study and published data, positive PD-L1 expression in tumor cells is associated with poor prognosis of PCa. Given the lack of association of PD-L1 expression in tumor cells with the routine clinical and pathological characteristics of the disease, it seems reasonable to include the status of PD-L1 expression in the current predictive nomograms for patients with PCa. The results may indicate the potential benefits of developing personalized approaches to PCa treatment, particularly with targeting a PD-L1/PD-1 signaling pathway in tumor cells.

Keywords: cancer-specific survival, metastasis-free survival, PD-L1, predictor, prostate cancer