For many men, prostate cancers are extremely slow-growing — patients often can be monitored periodically through blood tests, biopsies and MRI without necessarily needing treatment. Johns Hopkins experts have a precision medicine tool — called Active Care — that employs sophisticated statistical modeling and all of the patient’s prostate-specific antigen (PSA) protein level tests, biopsy results and other clinical information to estimate the chance that the cancer is slow-growing or more aggressive.