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Questions posted in the
The Urology Forum have been answered by urologists from Henry Ford Health System and by Dr. Kevin Pho.
Question Title: PSA testingForum: The Urology Forum
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I recently had a PSA test. Overall number was 1.1. However, the "free per cent" (not sure if this is the correct term or what this means) was 16 per cent. My urologist said this was low and could indicate that a biopsy should be performed to rule out cancer. What does this figure mean? Is it really possible to be cancerous when the PSA itself is only 1.1? Thank you very much. -------------------------------------------------------------------------------------------------------------------------------- Prostate specific antigen (PSA) has been in widespread use over the past several years as a screening tool to detect possible prostate cancer in individuals before the cancer becomes large enough to spread. This is because prostate cancer is insidious in its earlier stages and does not cause any symptoms, usually until it spreads and is too late to cure. The PSA test however is not perfect. Like any other laboratory test, there are conditions under which a person may have an elevated PSA in the absence of cancer. Some of these causes include a urinary tract infection, prostatitis (infection of the prostate), BPH (enlargement of the prostate that occurs with aging, etc. Therefore, the concept of free PSA was looked at as a possible way of differentiating patients with an elevated PSA and prostate cancer from those with an elevated PSA due to other causes. Usually some of the PSA in the blood is bound by protein. It is thought that prostate cancer produces more proteins which bind to PSA in addition to the normal binding, therefore leaving less unbound (or free) PSA circulating in the blood. Free PSA is a ratio of the free unbound PSA in the blood to the total PSA and is expressed as a percentage. Although much of this is still being examined by investigators, it has been observed that a free PSA less than 20% is most likely associated with the presence of prostate cancer, and a free PSA higher than 25% is usually not associated with prostate cancer, and between 20-25% is somewhat of a “gray zone” (indeterminate). The cutoffs mentioned above are not absolute, but vary from study to study. In an individual with a an elevated PSA (above 4.0), a free PSA of 16 percent increases the suspicion for prostate cancer. However, I’m not sure what this would mean in your case, since as urologists we look at the entire picture which includes age, African-American race, family history of prostate cancer (all of which are risk factors for prostate cancer) in addition to physical findings on digital rectal examination, and the overall trend of the PSA over a given period of time. Whether or not you should have a ultrasound guided prostate biopsy is really your decision. However, most urologists do not even check a free PSA if the total PSA is not elevated. If you have other risk factors as mentioned above or will worry not knowing why the free PSA is 16%, then it might be a good idea to go ahead with the biopsy. Your urologist might be better able to explain to you why he/she recommended the biopsy just on the basis of a free PSA, or you may want to obtain a second opinion from a urologist who can examine you in person and interpret your labs and specific situation. Wish you the best. This information is provided for general medical education purposes only. Please consult your physician for diagnostic and treatment options pertaining to your specific medical condition. More individualized care is available at the Henry Ford Hospital and its satellites (1 800 653 6568). Sincerely,
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