The overall goal of this method is to detect the gene copy number variation in serum or plasma samples.This method can help answer key questions in advanced prostate cancer field such as detection of markers useful to predict or monitor the spores reduction.The main advantage of this technique is that it is easy and fast to do.The implications of this technique extend toward therapy of advanced prostate cancer because androgen receptor gene copy number variation is a frequent event.Generally, individuals new to this method will struggle because the concentration and the quality of cell-free DNA is often lower than expected.For serum collection, work from five milliliter samples of whole blood and serum without anticoagulants maintained at four degrees Celsius.Start by centrifuging the samples for 15 minutes at 1, 000 g.The supernatant is the serum.Transfer it into two-milliliter tubes and discard the pellet.Unless the serum is processed immediately, freeze the samples at 80