Physicians have had ample time to investigate the clinical applications of prostate-specific acid phosphatase, but the same cannot be said of prostate-specific antigen. The latter appears to have advantages in monitoring patients with advanced prostate cancer. A high percentage of men with metastatic disease have an elevated level of prostate-specific antigen, and falling levels indicate a favorable response to treatment. Also, changes in prostate-specific antigen levels closely reflect tumor growth. Thus, prostate-specific antigen is gradually supplanting prostate-specific acid phosphatase as a tumor marker for prostate cancer. Transrectal ultrasound continues to generate excitement because of its potential uses in managing prostate cancer. Investigators are optimistic about continued success, despite some shortcomings of the procedure. Higher-frequency probes with greater resolution are now being used and may improve detection of subtle changes found in some tumors. Computer-assisted image analysis may also prove valuable.
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