Sipuleucel-T immunotherapy for castration-resistant prostate cancer. A systematic review and meta-analysis

INTRODUCTION Sipuleucel-T is a novel active cellular immunotherapy for the treatment of asymptomatic or minimally symptomatic metastatic castrate-resistant prostate cancer (mCRPC). It is assumed to be associated with less adverse events than conventional docetaxel-based chemotherapy. MATERIAL AND METHODS A systematic review of literature published between January, 1 1966 and February, 6 2012 was performed to assess the efficacy and safety of sipuleucel-T in patients with mCRPC. Databases were searched: Medline, EMBASE, Cochrane, CancerLit as well as ASCO and ESCO websites. RESULTS Three randomized clinical trials with a total of 737 participants fulfilled established criteria. The overall survival of patients who received sipuleucel-T in comparison to the control group was significantly longer with a hazard ratio (HR) of 0.73 (95% CI: 0.61-0.88; p = 0.001). Time to disease progression was not prolonged using sipuleucel-T compared to placebo, HR = 0.89 (95% CI: 0.75-1.05; p = 0.18). Relative benefit (RB) of serum PSA level reduction of at least 50% for sipuleucel-T compared to placebo did not meet statistical significance, RB = 1.97 (95% CI: 0.48-8.14; p = 0.38). The safety population consisted of 729 patients with mCRPC. Compared to the control group, the pooled relative risks (RR) of all adverse events - RR = 1.03 (95% CI: 1.00-1.05; p = 0.06), grade 3 to 5 adverse events - RR = 0.98 (95% CI: 0.79-1.22; p = 0.86) and cerebrovascular events - RR = 1.93 (95% CI: 0.73-5.09; p = 0.18) were not significantly higher for men treated with sipuleucel-T. CONCLUSIONS The use of sipuleucel-T prolonged the overall survival among men with mCRPC. No effect on time to disease progression was observed and the safety profile was acceptable.