Novel agents for castration-resistant prostate cancer: Early experience and beyond

Androgen deprivation therapy is the initial treatment for men with advanced prostate cancer. Almost all these patients eventually develop progressive castration-resistant prostate cancer despite an initial favorable response. Docetaxel was the first agent to show a survival benefit in patients with castration-resistant prostate cancer. After cancer progression on docetaxel, patients with castration-resistant prostate cancer had few therapeutic options. A better understanding of the mechanisms of resistance to androgen deprivation therapy has led to the development of novel agents with distinct mechanisms of action. Prospective, large-scale clinical trials have shown overall survival benefits with the hormonal agents abiraterone acetate and enzalutamide, the immunotherapeutic agent sipuleucel T, the chemotherapeutic agent cabazitaxel, and bone-targeted Ra-223. Although these agents provided clinical benefit, treatment for castration-resistant prostate cancer remains a major clinical challenge. We recognize many questions, such as methods to select patients for specific treatments, optimal sequencing and drug combinations, and means to overcome drug resistance. There is an urgent need to answer these questions and to establish better treatment strategies. The development of biomarkers that are predictive of treatment results is also required. The present article reviews new castration-resistant prostate cancer treatments, and discusses possible resistant mechanisms as well as potential drug combinations and optimal sequencing.