Marin M, et al. - In metastatic castration-resistant prostate cancer (mCRPC) patients, researchers assessed the link between androgen receptor (AR) variant 7 (ARV7) and AR full length (ARFL) expression pre-docetaxel treatment. They also looked at any pre- post-treatment changes in blood with docetaxel activity. Using quantitative reverse-transcription PCR, they analyzed ARV7 and ARFL mRNAs in peripheral blood mononuclear cells (PBMC) from patients with mCRPC . Pretreatment measurements were obtained, as well as for post-treatment measurements in a subset of patients. As a control, a cohort of patients treated with AR inhibitors (ARI) was analyzed. Overall 105 patients, 50 with treated with docetaxel and 55 with ARI, were included. In mCRPC patients, better clinical outcome and lower ARI benefit was reported in relation to high ARV7 expression and ARV7/ARFL ratio assessed in PBMC pre-docetaxel. Better outcome was also indicated by increase of ARV7 levels post-docetaxel exposure.