Disparities in Castration-Resistant Prostate Cancer Trials
Authors: Daniel E. Spratt, Joseph R. Osborne
Journal: Journal of Clinical Oncology (2015)

Disparities in health care delivery and outcomes are complex and longstanding. Many such disparities derive from limited access to health care, socioeconomic barriers, and cultural differences—each of which can result in minorities receiving suboptimal care, and ultimately in inferior outcomes. Recently published SEER data again underscore the undeniable disparities in cancer outcomes across ethnic groups. Understanding the drivers of these disparities is relevant for all subpopulations, but for black men with prostate cancer, this is especially true, as there are specific action items of timely importance. Black men with prostate cancer have a 2.5-fold greater risk of lethal prostate cancer compared with white men. Hispanic men with prostate cancer have demonstrated increased incidence rates and also have inferior survival rates when compared with white males. The increased incidence of advanced prostate cancer among Hispanic men, however, appears to be principally related to barriers in health care access (ie, education level, socioeconomic status, insurance status, and so on); when these factors are corrected for, no significant difference in lethal prostate cancer rates are found (odds ratio: 1.23 [95% CI, 0.73 to 2.08]). In contrast, black men appear to retain an independently increased risk for advanced disease despite corrections for access to health care (odds ratio 2.26 [95% CI, 1.43 to 3.58]). However, a major component of prostate cancer disparities is not simply whether patients have access to care, but also the dissemination of knowledge of the potential survival and quality of life benefit of optimal therapies. In the past decade, we have seen unprecedented progress in treatment options for men with prostate cancer. Since 2009, five therapies gained US Food and Drug Administration approval for improving survival in castration-resistant prostate cancer (CRPC): sipuleucel-T, abiraterone, enzalutamide, cabazitaxel, and radium223 chloride. Even as we affirm and celebrate this unprecedented progress, such strides raise additional questions. With an everexpanding array of treatment options, we now must ensure a pathway for all patients to receive optimal therapy. Wissing et al conducted a recent retrospective analysis of 17 clinical trials regarding prostate cancer prevention or treatment in six countries over the past 20 years. The analysis demonstrated a consistent under-representation of racial minorities in clinical trials, with approximately 5% of the studied patient population constituting black men. Unfortunately now more than ever, despite the new arsenal of cancer therapies for CRPC, representation of black men in these clinical trials to ascertain ethnic differences in clinical benefit is simply inadequate. Seven landmark phase III randomized controlled trials were performed to solidify US Food and Drug Administration approval of the five new therapeutic options for CRPC since 2009. As shown in Table 1, a total of 7,275 men were enrolled on these seven clinical trials. Each trial demonstrated improvements in overall survival and met their primary end point. This has generated a resurgence of hope for the nearly 30,000 men who suffer from lethal prostate cancer. However, only 3.3% (n 240) in total from all seven trials were black men. This rate should appear low to any reader, but the magnitude of under-representation is dramatically lower than would be expected. Recently, in response to these disparities, an action plan was implemented and reported from five National Cancer Institute (NCI)–designated cancer centers demonstrating an improvement in