Effectiveness of abiraterone acetate plus prednisone in chemotherapy-naive patients with metastatic castration-resistant prostate cancer in a large prospective real-world cohort: the ABItude study

Background: Real-world data on chemotherapy-naive patients with metastatic castration-resistant prostate cancer (mCRPC) treated with abiraterone plus prednisone are limited, largely deriving from small retrospective studies. Methods: ABitude is an Italian, observational, prospective, multicenter study of mCRPC patients receiving abiraterone plus prednisone in clinical practice. Chemotherapy-naive mCRPC patients were consecutively enrolled at abiraterone start (February 2016 to June 2017) and are being followed for 3 years, with evaluation approximately every 6 months. Several clinical and patients reported outcomes were examined. Results: In this second interim analysis, among 481 enrolled patients, 453 were evaluable for analyses. At baseline, the median age was 77 years and similar to 69% of patients had comorbidities (mainly cardiovascular diseases). Metastases were located mainly at bones and lymph nodes; 8.4% of patients had visceral metastases. During a median follow-up of 18 months, 1- and 2-year probability of radiographic progression-free survival were 73.9% and 56.2%, respectively; the corresponding rates for overall survival were 87.3% and 70.4%. In multivariable analyses, the number of bone metastases significantly affected radiographic progression-free survival and overall survival. During abiraterone plus prednisone treatment, 65% of patients had a > 50% prostate-specific antigen decline, and quality of life remained appreciably high. Among symptomatic patients according to the Brief Pain Inventory) (32%), scores significantly declined after 6 months of treatment. Overall, eight patients (1.7%) had serious adverse reactions to abiraterone. Conclusions: Abiraterone plus prednisone is effective and safe for chemotherapy-naive mCRPC patients in clinical practice.