Which Factors Predict Overall Survival in Patients With Metastatic Castration-Resistant Prostate Cancer Treated With Abiraterone Acetate Post-Docetaxel?

BACKGROUND: Abiraterone acetate (AA) increases overall survival (OS) in patients with metastatic castration-resistant prostate cancer (mCRPC) previously treated with docetaxel. However, survival time varies substantially between individuals. Our goal was to identify prognostic factors that better estimate OS. MATERIALS AND METHODS: This is a retrospective multicentric analysis of 368 patients with mCRPC starting AA with prednisone after docetaxel. Cox proportional hazards statistics were applied. A multivariate model was constructed based on significant univariate predictors by using a manual stepwise forward and backward selection strategy. Model performance was determined by using receiver operating characteristic (ROC) curves. RESULTS: Univariate analysis identified 20 significant OS predictors. A multivariate model was constructed, based on 220 patients, incorporating 5 independent risk factors for decreased OS at the time of AA initiation: hemoglobin < 12 g/dL (hazard ratio [HR] 2.02), > 10 metastases (HR 1.80), ECOG performance status ≥ 2 (HR 1.88), radiographic progression (HR 1.50), and time since diagnosis < 90 months (HR 1.66, all P < .05). Patients were stratified into 3 groups: good (0-2 risk factors, median OS 22.6 months), intermediate (3 risk factors, median OS 13.9 months), and poor prognosis (4-5 risk factors, median OS 6.2 months). The area under the ROC curve based on the event "death by the time of median OS (13.3 months)" was 0.736 (95% confidence interval 0.670-0.803). CONCLUSION: We identified 5 readily available risk factors independently associated with decreased OS. The resulting model may be used for patient counseling in daily clinical practice, as well as patient stratification in clinical trials.

Abiraterone acetate post-docetaxel for metastatic castration-resistant prostate cancer in the Belgian compassionate use program.

BACKGROUND: Abiraterone acetate (AA) is licensed for treating metastatic castration-resistant prostate cancer (mCRPC). Real-world data on oncological outcome after AA are scarce. The current study assesses efficacy and safety of AA in mCRPC patients previously treated with docetaxel who started treatment during the Belgian compassionate use program (January 2011-July 2012). PATIENTS AND METHODS: Records from 368 patients with mCRPC from 23 different Belgian hospitals who started AA 1000mg per day with 10mg prednisone or equivalent were retrospectively reviewed (September 2013-December 2014). Prostate-specific antigen (PSA) response (decrease≥50%), time to PSA progression (increase>50% over PSA nadir in case of PSA response/>25% in absence of PSA response), time to radiographic progression (on bone scans or for soft tissue lesions using Response Evaluation Criteria In Solid Tumors 1.1), overall survival and adverse event rate (Common Terminology Criteria for Adverse Events v4.03) were analyzed. Kaplan-Meier statistics were applied. RESULTS: Overall, 92 patients (25%) had an Eastern Cooperative Oncology Group performance status≥2. Median age was 73 years, median PSA was 103ng/dl. PSA response was observed in 131 patients (37.4%). Median time to PSA and radiographic progression was 4.1 months (95% CI: 3.6-4.6) and 5.8 months (5.3-6.4), respectively. Median overall survival was 15.1 months (13.6-16.6). Most common grade 3 to 4 adverse events were anemia (13.9%), hypokalemia (7.3%), fatigue (6.8%), and pain (6.3%). Median duration of AA treatment was 5.3 months (interquartile range: 2.8-10.3). The main study limitation is its retrospective design. CONCLUSIONS: These real-world data on post-docetaxel AA efficacy are in line with the COU-AA-301 trial. Importantly, incidence of severe anemia and hypokalemia is up to 50% higher than reported in previous studies.