Prognostic factors in men with metastatic castration-resistant prostate cancer (mCRPC) treated with enzalutamide (ENZA) or bicalutamide (BIC) in TERRAIN

Abstract

Background: In TERRAIN, men with mCRPC who had progressed during luteinizing hormone-receptor hormone agonist/antagonist (LHRHa) treatment or after bilateral orchiectomy were randomized to ENZA or BIC.1 This post hoc analysis explores pre-treatment factors associated with progression-free survival (PFS) and time to prostate serum antigen (PSA) progression (TTP) and a risk-group classification model based on the statistically and clinically predictive value of these factors. Methods: Data from randomizedmen in TERRAIN were analyzed. Cox regression analysis was used to identify pre-treatment factors associated with PFS and TTP as single or multiple variables in the model and to determine a risk-group classification. PSA, testosterone, lactate dehydrogenase (LDH), alkaline phosphatase (ALP), albumin (ALB), hemoglobin, neutrophil-lymphocyte ratio (NLR), LHRHa/orchiectomy start-date relative to diagnosis of metastasis, Eastern Cooperative Oncology Group performance status, Gleason score, disease location and prior antiandrogen use were used as continuous or categorical variables. Models were stratified by study treatment. Results: Data from 375 men were analyzed. PSA, LDH, ALP, ALB and disease location were prognostic factors for PFS and/or TTP in single and multiple variable models. NLR, hemoglobin and LHRHa start were prognostic factors in single variable models. For PFS and TTP, an efficient risk-group classification with three prognostic risk groups (best, intermediate and worst)was derived based on ALP, PSA and ALB. Median PFS for the best risk group (0-1) was 16.6 versus 3.3 months for the worst risk group (4) (hazard ratio 5.7; 95% confidence interval 4.0, 8.2). Conclusions: Three baseline laboratory parameters defined risk groups in a classification system and explained differential clinical benefits for men in TERRAIN for both ENZA-and BIC-treated groups.