The prognostic value of tumor PD-L1 status in patients with metastatic prostate cancer

Abstract

Background. New potential biomarker for patients with metastatic hormone-naive prostate cancer (PCa) might be detection of programmed death ligand 1 (PD-L1) expression in tumor which is associated with worsened results of treatment and decreased survival in patients with pancreatic cancer, lung cancer and other malignant tumors. Objective : to evaluate the prognostic value of positive tumor PD-L1 status on time to castration resistance (CRPCa) in patients with meta­static PCa receiving hormonal androgen deprivation therapy in first-line systemic treatment. Materials and methods. A total of 35patients with metastatic hormone-naive PCa receiving androgen deprivation therapy with luteinizing hormone-releasing hormone analogue and follow-up at N.N. Blokhin National Medical Research Center of Oncology were recruited in our prospective study. Tumor features of all patients were evaluated for PD-L1 expression on tumor cells by immunohistochemical studies of paraffin block sections obtained under the visual control of the pathologist using a set of monoclonal anti-PD-L1 antibody (28-8) (ab 205921) and Ventana BenchMark GXSlide staining system. Tumor tissue was obtained before starting androgen deprivation therapy. The expression level of PD-L1 >1 % in tumor cells was taken for the positive tumor PD-L1(+) status. Results . Median follow-up was 32.8 months. Positive tumor PD-L1(+) status was identified in 10 (28.6 %) cases. Median time to CRPCa was significantly lower in patients with PD-L1(+) status, than in negative PD-L1(—) status (21.44 vs. 49.12, p = 0.006 log rank test). Multi­variate Cox regression analysis confirmed independence prognostic value of PD-L1(+) associated with decreased time to CRPCa (hazard ration 5.95, 95 % confidence interval 1.97—17.99; p = 0.002), including in subgroup of patients with low-volume metastatic disease (hazard ration 7.33, 95 % confidence interval 1.81—29.60; p = 0.005). Discussion . Interaction of PD-1 receptors and its ligands PD-L1/PD-L2 is the key mechanism causing tumor immune escape and progression of the cancer. There are discussed certain ways of inducing PD-L1 expression and its prognostic value on aggressive nonmetastatic PCa. High frequency of positive PD-L1 status was revealed in rare histological subtypes of PCa associated with unfavorable prognosis and visceral metastasis. Conclusion. The results of our study demonstrated the positive tumor PD-L1 status as an independent unfavorable prognostic factorfor patients with metastatic hormone-naive PCa associated with decreased time to castration resistance, including in patients with low volume metastatic disease.