Impact of clinical trial participation on survival in patients with castration-resistant prostate cancer: a multi-center analysis

Background: Clinical trial (CT) participation may confer access to new, potentially active agents before their general availability. This study aimed to investigate the potential survival benefit of participation in investigational CTs of novel hormonal, chemotherapeutic, and radiopharmaceutical agents in patients with castration-resistant prostate cancer (CRPC). Methods: This multi-center, retrospective analysis included 299 consecutive patients with newly diagnosed, non-metastatic or metastatic CRPC between September 2009 and March 2017. Of these, 65 (21.7%) patients participated in CTs pertaining to systemic treatment targeting CRPC and 234 (78.3%) patients received pre-established, standard systemic treatment outside of a CT setting. The survival advantage of CT participation regarding cancer-specific survival (CSS) was investigated. Results: An Eastern Cooperative Oncology Group performance status (ECOG PS) >= 2 at CRPC diagnosis was found in a lower proportion CT participants than in non-participants (4.6% vs. 14.9%; p = 0.033). During the median followup period of 16.0 months, CT participants exhibited significantly higher 2-year CSS survival rates (61.3% vs. 42.4%; p = 0.003) than did non-participants. Multivariate analysis identified prostate-specific antigen and alkaline phosphatase levels at CRPC onset, Gleason score >= 8, ECOG PS >= 2, less number of docetaxel cycles administered, and non-participation in CTs as independent predictors for a lower risk of CSS. Conclusions: Patients diagnosed with CRPC who participated in CTs exhibited longer CSS durations than non-participants who received pre-established, standard systemic therapy outside of a CT setting. Our findings imply that CT participation is associated with CSS, and that CT participation should be offered to patients with CRPC whenever indicated.