A new blood test known as IsoPSA detects prostate cancer more precisely than current tests in two crucial measures — distinguishing cancer from benign conditions, and identifying patients with high-risk disease. By identifying molecular changes in the PSA protein, the findings of this study suggest that once validated, use of IsoPSA may reduce the need for biopsy, and may lower the likelihood of overdetection and overtreatment of nonlethal prostate cancer.