The role of surrogate markers in the management of men with metastatic castration-resistant prostate cancer.

Over the past year, the treatment of metastatic castration-resistant prostate cancer (mCRPC) was dramatically altered with the introduction of several novel agents. One of these agents, the cancer immunotherapy sipuleucel-T, represents a major change in the treatment paradigm for patients with mCRPC. While immunotherapies such as sipuleucel-T are associated with a significant improvement in overall survival, many questions remain regarding their use. Specifically, there are questions as to which endpoints should be used to measure benefit with immunotherapy. Clinical trials of sipuleucel-T demonstrated that the traditional endpoints normally used in mCRPC trials, such as progression-free survival, are not good measures of response with immunotherapy. However, measurement of overall survival is difficult in the clinical trial setting. There is now a major interest in the identification of surrogate biomarkers of survival that could allow the benefit of novel agents to be more precisely determined. Many potential biomarkers have been identified, often from studies showing their prognostic potential. In this roundtable, experts discuss the role of biomarkers in measuring response to immunotherapy for men with mCRPC.