DANIEL P. PETRYLAK, MD: It's important for us to select which patient is going to have very aggressive disease or which patient simply can be cured with local treatment.
ANNOUNCER: Sorting out how aggressive a particular prostate cancer is likely to be is not easy.
JAMES A. EASTHAM, MD: One of the difficulties that we have is identifying or characterizing a cancer as being slow growing or fast growing. That's one of the active areas of research, is to try to identify newer ways to characterize a cancer, because you would obviously treat a faster growing cancer perhaps aggressively or as a slower growing cancer, you might even be able to watch.
ANNOUNCER: Doctors traditionally use three factors in trying to determine how aggressive a particular cancer might prove to be.
DANIEL P. PETRYLAK, MD: Gleason score is a measure as to how aggressive a cancer is. So if we look at the cancer under the microscope, the less aggressive lesions appear to be more organized, and the most aggressive lesions almost look like spaghetti. They're very, very disorganized. So the Gleason score is a way of measuring the degree of organization and disorganization. The more disorganized the higher the Gleason score and hence the higher the chance of the cancer coming back.
ANNOUNCER: The second factor is whether or not the disease has spread to nearby lymph nodes. These glands, which are part of the immune system, are often the first place prostate cancer spreads when it has metastasized.