Since the mid-1980’s, urologists have been very lucky to rely on one of the best serum markers available in medicine, prostate-specific antigen (PSA), for the diagnosis of the most common solid cancer in men, prostate cancer. There is, however, a critical need to improve the specificity of serum PSA in order to decrease the number of unnecessary prostate biopsies. Indeed, currently most men with serum PSA levels between 2.5 and 10 ng/mL, depending on their age and percent free PSA are recommended for a biopsy, even though 65% to 75% of them do not have prostate cancer.1