Androgen deprivation (hormonal) therapy is often administered to men with advanced prostate cancer. However, after a period of time genetic mutations can occur in the prostate cells which then promote tumor growth. A new way to monitor how a man’s cancer is changing during treatment and which could help identify the stage at which some drugs stop being effective would be very useful. A new blood test which measures DNA from these circulating prostate cells could reveal when existing treatment stops working and harmful, hormone-resistant tumor cells begin proliferating. At that point, existing treatment could be stopped and the next best treatment option could be administered. Measuring the circulating tumor cell’s DNA could conceivably personalize treatment for an individual based on the tumor cell mutations detected. According to a study published in the September 17th Science Translational Medicine and summarized in the September Prostate Cancer Foundation (PCF) Research NewsPulse, such a test could be a less invasive and less expensive way to monitor the emergence of treatment-resistant prostate cancer. This published preliminary study was small (16 men) and larger studies are in order.