Four times a year I go into one of the Southern Medical Laboratories offices and have a sample of blood taken. Someone in a lab somewhere then measures my levels of cholesterol, blood sugar and uric acid. And they look for the one I am really interested in: my levels of Prostate Specific Antigen. PSA is produced only by the prostate gland, and seeing as I have had mine removed, if there is any PSA in my bloodstream it can have come from only one source: prostate cancer cells that have drifted off through my lymph system and are now lodged and growing in some unknown part of my body. About three years ago my PSA levels, while still comparatively low, were increasing alarmingly, doubling every four months or so in a pattern which, if not dealt with would have proven imminently fatal. My urologist started me on a course of hormone injections which reduced the levels immediately to zero, where they have stayed since. While the hormones deal to the overwhelming majority of cancer cell