The PSA Blood Test
PSA plays a variety of roles, the most familiar being screening to detect prostate cancer. PSA also helps to define the Stages of Blue. 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 or not.
Prostate Cancer Screening is Controversial
PSA screening often leads to the detection of small, essentially harmless cancers. Doctors and patients frequently overreact, rushing into unnecessary radical treatment. Over-treatment of tiny cancers became such a big problem that in 2011 a government-sponsored team of experts, the U.S. Preventive Services Task Force, issued a warning against routine PSA screening. This recommendation was recently rescinded, acknowledging the value of PSA screening in well-informed patients.
Scans Measure the Size of the Prostate
Imaging with ultrasound or MRI improves the accuracy of PSA. Let me explain why. Many men run high PSA levels from a condition called BPH that is totally unrelated to cancer, creating concerns that prostate cancer might be present. However, BPH is benign enlargement of the prostate gland, a common phenomenon associated with aging that is unrelated to prostate cancer.
The formula for determining when the PSA is outside the range expected when the enlarged gland is taken into account is as follows: PSA is “normal” when your PSA is approximately the same number as when your prostate volume is divided by 10. For example, a noncancerous 30cc prostate should have a PSA of around 3.0; for a noncancerous 50cc prostate the PSA should be around 5.0. A man’s PSA with a 100cc prostate will be approximately 10. PSA is only abnormal (the official term is a “high PSA density”) when it’s 50 percent higher than would be expected, based on the prostate’s size. For example, a man’s PSA is abnormal if he has a 30cc prostate and his PSA is above 4.5. An abnormal PSA for a 50cc prostate is above 7.5. For a 100cc gland, PSA would need to be above 15 to be suspicious.
PSA Density
Doctors use a less intuitive way to do the exact same calculation. Instead of dividing PSA into the gland volume, they do the opposite. They divide the gland volume into the PSA. Using this inverted formula, an abnormal PSA relative to a specific-sized prostate is anything above 0.15. Men above 0.15, using this formula, are said to have a high “PSA Density.”
A Suggested PSA Screening Protocol
PSA is inexpensive and easily accessible. Therefore, it is reasonable to start checking PSA in men over the age of 40. The only precaution is to go slow and do careful research about next steps if the PSA is found to be elevated
Using PSA to Stage Prostate Cancer
Despite the controversies that surround the use of PSA for screening, there are no controversies about using PSA for cancer staging. Men with a higher PSA at the time of diagnosis, above 10 or 20 for example, are more likely to have cancer that has spread outside the gland.
PSA to Monitor for Cancer Relapse After Surgery or Radiation
Cancer recurrence can be 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 well below 1.0. When there is a cancer recurrence after previous surgery or radiation, 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, a 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 therapies for Royal—Xofigo and Provenge—clearly prolong life but may show little or no impact on PSA
Conclusion
PSA results must be utilized 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.