Prostate cancer is easy to detect with a rectal exam or a PSA (prostate-specific antigen) test. The test measures the level of protein in the blood produced by the prostate. If the levels are elevated, it could be an indicator of a simple infection or a tumor. This is why it's important for men to know what their normal PSA number is, says Dr. Mehmet Oz, Vice-Chair and Professor of Surgery at Columbia University. "You've got to get a baseline number. One of the big mistakes men get is they never get started. If you're 40 years of age, you ought to know what your PSA is."