Sequential therapies in castration-resistant prostate cancer

An unprecedented large number of agents capable of prolonging survival is presently available for patients with castration-resistant prostate cancer (CRPC) [1,2]. Survival expectancy of a patient with newly diagnosed CRPC has approximately doubled since the approval of docetaxel, although it still appears to be poor in selected populations [3,4], such as those with primary refractoriness to docetaxel [5]. US FDA- and EMA-approved agents now include immunotherapy agent sipuleucel-T, CYP17A inhibitor abiraterone, antiandrogen receptor enzalutamide, cytotoxic agent cabazitaxel and radiopharmeceutical agent radium-223. These agents were approved in different settings. While sipuleucel-T was mainly tested in minimally symptomatic, chemotherapy-naive patients, abiraterone, enzalutamide and cabazitaxel were tested in patients pretreated with docetaxel. Radium-223 was approved in patients who were either ineligible to or refused or had already received docetaxel, and had symptomatic diffuse bone metastases. Although abiraterone proved to prolong progression-free survival in chemotherapy-naive patients, with a statistically significant improvement in overall survival that did not satisfy the statistical boundaries required by the study design, the potential detrimental effect on survival that postponing docetaxel in a population of metastatic CRPC might have was not adequately accounted for in this trial, and an opportunity to test sequential therapies was missed [6]. With multiple available effective agents, their optimal sequential use, their use in selected populations and the early assessment of efficacy in individual patients are three main issues.

Click here to view full article.