Clinical Variables Associated With Overall Survival in Metastatic Castration-Resistant Prostate Cancer Patients Treated With Sipuleucel-T Immunotherapy

Background Sipuleucel-T is an autologous cell-based cancer immunotherapy for men with asymptomatic or minimally symptomatic metastatic castration-resistant prostate cancer (mCRPC). Its approval by the Food and Drug Administration was based on demonstration of an overall survival (OS) benefit in randomized placebo-controlled phase III trials. However, treatment was associated with a prostate-specific antigen (PSA) decline in only a small minority of patients. Understanding the clinical factors that are associated with OS could help guide treatment decisions, including patient selection and the timing of sipuleucel-T relative to other therapies. Patients and Methods We retrospectively identified 94 mCRPC patients treated with sipuleucel-T from April 2010 to April 2016. The Kaplan-Meier method was used to estimate the distribution of OS. Univariate and multivariate Cox proportional hazard modeling was used to identify the prognostic factors for OS. Results With a median follow-up of 24.9 months, the median OS was 34.9 months. On multivariate analysis, Eastern Cooperative Oncology Group performance status, pretreatment PSA doubling time, and previous abiraterone and/or enzalutamide were significant prognostic factors for OS. Conclusion A poorer baseline performance status, faster disease pace measured by the PSA doubling time, and previous novel androgen signaling inhibitor exposure could be important prognostic considerations for the treatment of mCRPC patients with sipuleucel-T. Further studies are needed to validate these findings.