Abiraterone acetate and orteronel are two CYP-17 inhibitors that have been studied in prostate cancer. They have shown relevant toxicities, including fluid retention/oedema, hypokalaemia, hypertension, liver function test abnormalities and cardiac events. The goal of this study was to determine the risk of special adverse events related to CYP- 17 inhibitor in patients with metastatic castration-resistant prostate cancer (CRCP). Summary data from four randomized phase III trials comparing CYP-17 inhibitors and prednisone versus placebo and prednisone in metastatic CRCP patients were meta-analysed. Pooled risk ratios (RRs) for the risk of all-grade and grade 3-4 adverse events of special interest were calculated. Data from 4916 patients (2849 in the AA experimental arm; 2067 in the control arm) were analysed. The incidence of grade 3-4 adverse events was never more than 10% of the patients. However, compared with placebo, the CYP-17 inhibitor significantly increased the all-grade events of hypertension (RR = 1.53; 95% CI = 1.3-1.8; p