system
Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
user
Best investigation for prostate cancer is -
assistant
The correct answer is  Answer- C. PSA velocityFor men with a PSA above 4, PSA velocity of more than .75 ng/ml year is suggestive of Ca.While for those with lower PSA levels, rates above 0.5 ng/ml per year should be used to advise biopsy.