Prognostic Value of Automated Bone Scan Index in Men With Metastatic Castration-resistant Prostate Cancer Treated With Enzalutamide or Abiraterone Acetate.

Abstract

Bone scan index (BSI) is an objective tool for quantifying bone metastasis load. We assessed its prognostic usefulness in patients with metastatic castration-resistant prostate cancer (CRPC) treated with enzalutamide (ENZ) or abiraterone acetate (AA). We analyzed 40 patients who received ENZ or AA treatment (ENZ/AA) for metastatic CRPC. The Cox proportional hazards model and a C-index were used to investigate associations between overall survival (OS) and BSI, and patient age, prostate-specific antigen, time to CRPC, previous docetaxel use, and pain. Median OS after ENZ/AA was 17.8 months. All patient deaths (n= 19; 47.5%) were from prostate cancer. In multivariate analysis, decreased BSI was an independent predictor for longer OS (hazard ratio, 8.97; P= .011). Inclusion of BSI improved the C-index from 0.721 to 0.792 in predicting OS after ENZ/AA. Decreased BSI after ENZ/AA independently predicts longer OS.