3089 - Prognostic factors in men with metastatic castration-resistant prostate cancer (mCRPC) treated with enzalutamide (ENZA) or bicalutamide (BIC) in TERRAIN

Background

In TERRAIN, men with mCRPC who had progressed during luteinising hormone receptor hormone agonist/antagonist (LHRHa) treatment or after bilateral orchiectomy were randomised to ENZA or BIC. 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 randomised men in TERRAIN were analysed. 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), haemoglobin, neutrophil-lymphocyte ratio (NLR), LHRHa/orchiectomy start date relative to diagnosis of metastasis, ECOG performance status, Gleason score, disease location and prior anti-androgen use were used as continuous or categorical variables. Models were stratified by study treatment.

Results

Data from 375 men were analysed. PSA, LDH, ALP, ALB and disease location were prognostic factors for PFS and/or TTP in single and multiple variable models. NLR, haemoglobin and LHRHa start were prognostic factors in single variable models. For PFS and TTP, an efficient risk group classification with three prognostic risk groups was derived based on ALP, PSA and ALB (table). Median PFS for the best risk group (0–1) was 16.6 months vs 3.3 months for the worst risk group (4) [hazard ratio, 5.7; 95% confidence interval 4.0, 8.2].