Blood Tests May Identify Patients Less Likely to Benefit from Hormone Therapies

Blood Tests May Identify Patients Less Likely to Benefit from Hormone Therapies
Two new blood tests that detect a variant of the androgen receptor — a protein that binds male hormones called androgens — may help to predict those advanced prostate cancer patients who would not benefit from anti-androgen therapies, new research suggests. The tests, which are called “liquid biopsies,” may help guide care toward more effective treatments. The research, “The PROPHECY trial: Multicenter prospective trial of circulating tumor cell (CTC) AR-V7 detection in men with mCRPC receiving abiraterone (A) or enzalutamide (E),” was recently presented at the 2018 American Society of Clinical Oncology (ASCO) annual meeting in Chicago. A variation of the androgen receptor, called AR-V7, has been linked to poor responses to drugs like Zytiga (enzalutamide) and Xtandi (abiraterone) in patients with castration-resistant prostate cancer.  This happens because the medicines target a domain of the receptor that is missing in the AR-V7 version. (Castration resistant means the disease progresses despite androgen depletion therapy.) Researchers have developed tests that detect AR-V7 in tumor circulating cells — cells that shed from the tumor or metastasis into circulation – but whether these could be used to predict the effectiveness of Zytiga and Xtandi in metastatic castration-resistant prostate cancer is unclear. Investigators at the Duke Cancer Institute designed a multi-center study — called PROPHECY (NCT02269982) — to evaluate how well the blood tests predict the effectiveness of these hormone therapies. A total of 118 men were enrolled at five medical centers to provide external validation for the two tests. One is marketed by Epic Sciences and Genomic Health and is called AR-V7 CTC nuclear protein test, while the other w
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