Background: The Prostate Cancer Registry is the first prospective, international observational study in mCRPC documenting characteristics and management in routine clinical practice, independent of treatment used. The study began in June 2013 enrolling > 3000 mCRPC patients (pts) followed for ≤ 3 years. Methods: Source-verified data were collected from men with documented mCRPC initiating a new mCRPC treatment or in surveillance. A history of disease progression despite surgical or chemical ADT was confirmed in all pts. This interim analysis reports baseline characteristics, treatments and outcomes in pts with no prior mCRPC treatment. To evaluate comparative effectiveness between treatments, propensity scoring (PS) methods were used to reduce effects of confounding. Results: Of 1906 evaluable pts with ≥ 12-month follow-up, the most commonly initiated first-line mCPRC treatments (n ≥ 50) were abiraterone acetate + prednisone (AA, n = 472), enzalutamide (ENZ, n = 98) or docetaxel (DOC, n = 382). Baseline characteristics, time to progression (TTP) and prostate-specific antigen (PSA) response ( ≥ 50% decrease within 6 months) are shown in the table below. Conclusions: In this real-world study, pts receiving DOC as their first mCRPC treatment had more severe disease at entry and a trend for shorter TTP vs androgen inhibitors. TTP results are consistent with those in randomised clinical trials for AA and ENZ. Clinical trial information: NCT02236637

^aData are % pts with measurement/record TTP was longer for AA vs DOC and ENZ vs DOC (PS adjusted p = 0.008 and p = 0.011); no significant difference was seen for AA vs ENZ (p= 0.491)