Bone scan index at baseline as a tool for predicting hematologic toxicity in metastatic castration-resistant prostate cancer patients eligible for radium-223 treatment.

e16513Background: The prognosis of castration-resistant prostate cancer with skeletal metastasis (CRPCSM) is poor. The ALSYMPCA trial led to the approval of radium-223 (Ra223) in such patients. Factors that could predict hematologic toxicities associated with Ra223 remain poorly defined. We analyzed the utility of bone scan index (BSI) at baseline (BSI-B) as a predictive marker for such toxicities. Methods: This is a retrospective study of CRPCSM patients without visceral metastasis who received Ra223 at Roswell Park Cancer Institute from 2013 to 2015. BSI was defined utilizing the estimation of a numerical index (max, 70.8% for diffuse skeletal involvement) that expresses the fractional involvement of each bone by tumor. BSI-B values were classified into third quartile ( > Q3). The associations between BSI-B and different hematologic parameters [hemoglobin (Hgb), platelets (Plt), absolute neutrophil count (ANC)] over the Ra223 trea...