Many patients are likely to die of intercurrent illness rather than of prostate cancer.
Thus, the patient's age and coexisting medical problems are primary considerations in determining treatment options. Tumor stage is clearly important in anticipating the clinical course of a given patient's disease. DNA ploidy may be an independent indicator of prognosis for some tumor stages as well, although it is not often used clinically at present. PSA density, defined as the ratio of PSA level to prostatic volume as determined by transrectal ultrasound, may be another valuable indicator. With the information available, an effort can be made to predict the behavior of newly diagnosed prostate cancer.