Results, too, vary widely, depending on such factors as the stage and grade of tumors, the length of time after treatment a patient is followed, and the criteria used to define cancer control. Many studies just look at results of prostate biopsies—not incorporating other important signs that something is wrong with the prostate, like a lump that can be felt in a digital rectal exam, or symptoms of urinary obstruction (from a tumor that is large enough to disrupt urinary flow), or changes in PSA or acid phosphatase levels. It’s significant that the best results for cancer control—a zero percent failure rate in some cases— generally come from the studies with the shortest follow-up time. How can an eighteen-month study possibly be as thorough, or ultimately helpful, as a ten-year study?
One long-term study predicted a local relapse rate (where cancer returns to the prostate or surrounding tissue) of 52 percent at fifteen years, with a failure rate during this time of about 11 percent a year. The average time it took for local recurrence to be diagnosed was nine years.
With external-beam radiation treatment, the five-year mark after treatment is a big milestone; in most cases, if cancer’s going to come back, it happens before then. But with interstitial brachytherapy, in a significant number of men cancer comes back after five years. In one study, for instance, only 57 percent of the men who ultimately would have a relapse were diagnosed within five years. In another study, it took at least six to eight years before half of the men experienced local relapse.