Immunotherapy in Prostate Cancer: Recent Advances and Future Directions

Abstract

In recent years, immunotherapy has been proposed for the treatment of asymptomatic or minimally symptomatic metastatic castrate-resistant prostate cancer (PCa). Clinical trials using Sipuleucel-T have demonstrated a survival benefit in PCa patients, suggesting that this cancer is linked to a limited immune response. However, the outcome of PCa treated with immune therapeutics has limited benefits in monotherapy: novel vaccination approaches and immune checkpoint blockade gave disappointing results. Several combinations of therapies, such as novel cancer vaccines or checkpoint inhibitors with different immunotherapeutic agents, combined with hormone therapy (enzalutamide, abiraterone acetate), radiotherapy or radium-223, DNA-damaging agents (olaparib), or chemotherapy (docetaxel) hold great promise for eliciting an immune response and improving clinical outcomes in PCa. The goal of immunotherapy is to overcome immunosuppression and destroy cancer cells, or at least to induce those pathways that go back from ‘the escape phase to equilibrium phase’ according to the definition of cancer immunoediting. The aim of this review is to analyse the immune responses during PCa progression and to present the current data regarding immune therapies for PCa.