ARV7 and ARFL mRNA in blood to predict androgen receptor inhibitors and docetaxel response in castration-resistant prostate cancer patients.

207Background: The constitutively active androgen receptor (AR) variant 7 (ARV7) has been associated with AR inhibitors (ARI) resistance, while its role predicting taxanes response remains controversial. We investigated the association between ARV7 and AR full length (ARFL) expression pre-docetaxel treatment and changes pre- post-treatment in blood with docetaxel activity in metastatic castration-resistant prostate cancer (mCRPC) patients. Methods: ARV7 and ARFL mRNAs were tested by quantitative reverse-transcription PCR in peripheral blood mononuclear cells (PBMC) from mCRPC patients. Measurements were performed before docetaxel treatment and in a subset of patients also post-treatment. A cohort of patients treated with ARI was also included as a control. Results: We included 105 patients: 50 with treated with docetaxel and 55 with ARI. In 28 patients ARV7 and ARFL were evaluated pre and post-docetaxel. High ARV7 correlated with longer PSA-PFS (HR 0.42; 95%CI 0.18-0.99; P= 0.049), radiologic (RX)-PFS (HR...