PSA plays a variety of roles, the most familiar being screening to detect prostate cancer at an early stage. Another role of PSA is to detect cancer relapse after surgery or radiation. Lastly, rises or declines in PSA after hormone therapy or chemotherapy help determine whether a treatment is working. 

PSA to Monitor for Cancer Relapse After Surgery or Radiation

Cancer recurrence is signaled by a rising PSA. Normally after surgery, the PSA should drop to undetectable levels. Even a small rise in PSA is significant. After radiation, the PSA should generally remain under 1.0, though exceptions certainly exist. The rate of PSA doubling is a very important indicator of the recurrent cancer’s aggressiveness. For example, recurrences associated with PSA levels that require over 12 months to double are low-grade. On the other hand, PSA that doubles in less than three months signals aggressive disease.

Determining the Response to Hormone Therapy or Chemotherapy

A PSA decline of more than 30 percent within a couple of months of starting chemotherapy provides a strong indication that the treatment is working. However, not every treatment, even when it is effective, makes an impact on PSA. Two new therapies for Royal—Xofigo and Provenge—clearly prolong life but may show little or no impact on PSA.


PSA results must be interpreted in the context of each patient’s overall circumstances by an expert with experience in managing prostate cancer. Unexpected PSA results should always be retested. Laboratory errors are possible and variations also occur between labs. 


Stanley Brosman, MD is board-certified in urology.  Former chief of urology at UCLA/Harbor General Hospital, a clinical professor of surgery/urology at UCLA,. and associate director of urologic oncology at John Wayne Cancer Institute. He is past president of the urology section of the California Medical Society and past president of the Los Angeles Urologic Society. He is author or coauthor of more than 80 peer-reviewed scientific articles and over 50 book chapters or monographs. He practices urology with a focus on prostate cancer in Santa Monica, California, at the Pacific Urology Institute.

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