Comprehensive evaluation of PD-L1 expression in primary and metastatic prostate cancer
Menée à partir de l'analyse immunohistochimique d'échantillons tumoraux prélevés sur 539 patients atteints d'un cancer primitif de la prostate, cette étude évalue, en fonction de ces caractéristiques (adénocarcinome acineux ou canalaire, carcinome à petites cellules, cancer métastatique de la prostate résistant à la castration), l'expression de PD-L1
Antibodies targeting the PD-1/PD-L1 interaction have shown clinical activity in multiple cancer types. PD-L1 protein expression is a clinically validated predictive biomarker of response for such therapies. Prior studies evaluating the expression of PD-L1 in primary prostate cancers have reported highly variable rates of PD-L1 positivity. In addition, limited data exist on PD-L1 expression in metastatic castrate-resistant prostate cancer (mCRPC). Here we determined PD-L1 protein expression by immunohistochemistry using a validated PD-L1 specific antibody (SP263) in a large and representative cohort of primary prostate cancers and prostate cancer metastases. The study included 539 primary prostate cancers comprised of 508 acinar adenocarcinomas, 24 prostatic duct adenocarcinomas, seven small cell carcinomas, and a total of 57 cases of mCRPC. PD-L1 positivity was low in primary acinar adenocarcinoma with only 7.7% of cases showing detectable PD-L1 staining. Increased levels of PD-L1 expression were noted in 42.9% of small cell carcinomas. In mCRPC, 31.6% of cases showed PD-L1–specific immunoreactivity. In conclusion, in this comprehensive evaluation of PD-L1 expression in prostate cancer, PD-L1 expression is rare in primary prostate cancers, but increased rates of PD-L1 positivity are observed in mCRPC. These results will be important for the future clinical development of PD-1/PD-L1 targeting therapies in prostate cancer.