Baseline analysis of circulating tumor cell (CTC) enumeration and androgen receptor (AR) localization in men with metastatic castration-resistant prostate cancer (mCRPC) in TAXYNERGY.

5031 Background: Microtubule-targeted therapy with taxanes is the only chemo with survival benefit in advanced PC. Emerging molecular evidence suggests sensitivity/resistance to taxanes may relate to the ability of microtubules to inhibit AR nuclear trafficking. CTCs represent a real-time biomarker for molecular testing including taxane-induced microtubule stabilization and AR nuclear localization. Methods: TAXYNERGY is an international, multicenter phase 2 trial in progressive, chemo-naive mCRPC men randomized (2:1) to docetaxel or cabazitaxel. Pre-treatment CTCs were enriched from 1 ml blood via a prostate-specific microfluidic device, enumerated, and analyzed by multiplex confocal microscopy for AR cellular localization. Nuclear AR % was calculated by integrating fluorescence intensity in the total cell and nuclear area. Bivariate correlations and multiple regressions examined associations between baseline characteristics and % nuclear AR or CTC count. Results: 63 men were randomized (median age 70 [ra...