Dear Abby, my PSA…

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If you are a reader of this blog, it is likely that you or a close friend/relative has dealt with or are dealing with prostate cancer. Hence, you have become the “expert” in your family or book club or similar for people who know your story. One of the most frequent questions I encounter in such circumstances is a question about someone’s recent PSA. As an example, an 86 year old otherwise healthy cardiologist recently called me asking what to do about his  PSA that had gone from 4-ish to 6-ish during the last 2 years.

There are a few generalizations that seem to apply to most of these queries. First, the PSA increases at a fairly predictable rate with age. As a crude rule of thumb, I tell patients/friends that it should be less than 2 when you are 50, less than 3 when you are 60, and less than 4 when you are 70. A recent article in JAMA illustrates this point nicely. In the PLCO cancer screening trial, 10,968 men aged 55-60 had a baseline PSA drawn and were then followed with various screening strategies for prostate, colon, or lung cancer. Among the men with baseline PSA of <0.99, the incidence of developing clinically significant prostate cancer in the next 13 years was only 1.5%, whereas if their baseline PSA was 2-2.99, the chances increased to 10.6%. The authors concluded that ” These findings suggest that repeated screening can be less frequent among men aged 55 to 60 years with a low baseline PSA level (ie, <2.00 ng/mL) and possibly discontinued among those with baseline PSA levels of less than 1.00 ng/mL.” What to do for my octogenarian cardiologist friend is more complicated, of course.

A second generalization is that if someone has chosen to follow his PSA more closely, say on an annual basis, because they have read enough about screening to feel that regardless of the controversy, they wish to do so, they should plot their data. A column of numbers is much harder to interpret than a visual graph. There is an easy way to do this by entering the data on a website like this one: Doubling-Time.  It is also important to realize that different labs may give slightly different values on the same patient – particularly challenging if one is trying to torture the data in the lowest ranges of detectability (<0.2).

Thirdly, and related to the plotting approach, for any given patient with known metastatic prostate cancer, the absolute value of PSA may be less important than the rate of change (doubling time). A rising PSA that goes from 3 to 6 in 6 months is of greater concern than someone with a PSA going from 150 to 160. Of course having a lower value generally means a lower cancer burden, but I once had a patient enjoy elk hunting during the later stages of his disease with a PSA over 2000. He had relatively few symptoms in spite of his advanced disease.

Lastly, and related to my aging cardiologist friend, there’s a lot more to know than the PSA in most cases. When I asked him what his urinary habits were (unchanged) and what his rectal exam revealed (he hadn’t had one), I suggested he should visit a urologist for a more complete picture. If you biopsied his prostate, there is probably >50% chance of finding cancer at his age, but the key question is whether it would be a “clinically significant” cancer (Gleason score >3+3=6, or multiple cores positive etc.) In addition, one now has the opportunity to do pre-biopsy tests such as Select MDx, PHI, or ExoDx with newer tests being developed all the time to try and NOT find patients with low risk disease who might never need any sort of treatment.

So, at your next cocktail party when a friend asks about PSA, you can gently explain the complexities you are all too familiar with, and hopefully guide them in the right direction. And if you are interested in more blogs, I recently discovered Snuffy Myers’ blog site, Prostapedia, that has numerous blogs from highly respected prostate experts with great ongoing updates. Happy New Year and most importantly EXERCISE!

 

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Filed under General Prostate Cancer Issues

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