Another, separate look at the value of mass, PSA-based screening


For those who are really “into” the probabilistic statistics of prostate cancer decision analysis, we recommend a recent article in the journal  Medical Decision-Making.

Quite independently of the USPSTF recommendation issued a little more than a week ago,  Zhang et al., report that even if mass, population-based screening of uninformed men through use of PSA testing on an annual basis for risk of prostate cancer really is in the individual interests of either the patients or of society as a whole, it is more likely to be so in younger than in older males.

Zhang et al. based their analytical model on data from 11,872 men and 50,589 PSA test results carried out in Olmsted County, Minnesota, between 1993 and 2005. This is a largely white, and much-studied, Midwestern community that includes the Mayo Clinic in Rochester, MN. It is therefore a pretty safe bet that the vast majority of the 140,000+ residents of Olmsted County who might have been diagnosed and needed treatment for prostate cancer over this 12-year period were getting it at the Mayo Clinic.

The authors used the available data to construct a Markov model of the trade-offs between the hypothetical benefits of early detection through screening as compared to the cost of screening and the loss of the patients’ quality of life due to screening and treatment. This type of Markov modeling is complex, but is comparable to the Markov modeling systems used several years ago by Albertsen and his colleagues to show that men diagnosed with low Gleason scores and low-risk prostate cancer were at low risk for prostate cancer-specific mortality over periods of up to 20 years. We have no intention of trying to explain the mathematical details!

Zhang and his colleagues set out to classify their results into two sets of outcomes, based on:

  • The perspective of the individual patient, i.e.,
    • The desire to maximize expected quality-adjusted life years (QALYs)
  • The perspectives of society as a whole, i.e.,
    • The desire to maximize the expected monetary value based on societal willingness to pay for QALYs
    • The desire to minimize the cost of PSA testing, prostate biopsies, and treatment

They were able to show the following:

  • From the patient perspective,
    • Optimal policy appears to suggest stopping all PSA testing and biopsies at age 76 years.
    • The incremental benefit of an optimized model for screening over the traditional guideline of annual PSA screening with a  threshold of 4.0 ng/ml for biopsy is only 0.165 QALYs per person.
  • From the societal perspective,
    • Optimal policy appears to suggest stopping all PSA testing and biopsies at age 71 years.
    • The incremental benefit of an optimized model for screening over the traditional guideline of annual PSA screening with a threshold of 4.0 ng/ml for biopsy is only 0.161 QALYs per person.
  • PSA screening based on traditional guidelines (i.e., a PSA of 4 ng/ml) is worse than no screening at all.

The authors conclude that:

  • PSA testing done under traditional guidelines under-performs and therefore under-estimates the potential benefit of screening.
  • Optimal screening guidelines differ significantly depending on the perspective of the decision-maker.

In other words, among other things, the authors are telling us is that screening according to traditional guidelines really is worse than no screening at all, and that even screening using their optimized model is little better than traditional screening (an improvement of less than 2 quality-adjusted life months on average).

The authors are careful not to make any absolute recommendations about whether, in principle, widespread, PSA-based screening of men for risk of prostate cancer is a “good” or a “bad” idea. After all, this is “just” a sophistical mathematical model and analysis. However, The “New” Prostate Cancer InfoLink does find it very interesting that this new article, like others before it, has the potential be be used as “evidence” by groups on both sides of the USPSTF recommendation debate.

It makes perfect sense to The “New” Prostate Cancer InfoLink that if screening for risk of prostate cancer is going to work, it will work best in the men who are likely to get the greatest benefit (i.e., younger men at high risk for clinically significant prostate cancer). If one extends that logic, then the idea of men getting a baseline PSA at 40 or thereabouts as a first step toward long-term risk management makes perfect sense … but annual PSA screening for every man between 50 and 75 years of age makes very little sense at all … because most of those men will be shown early on to be at minimal risk for clinically significant prostate cancer.

7 Responses

  1. OK. So let’s test every 40-year-old man for a baseline and, depending on the results, conduct an annual or bi-annual test until 70 or 75, then stop screening at 75 (or 70) unless the patient asks to be tested.

    Since, by now, he has been tested for 35 (or 30) years I would assume most people will ask to continue, but this is their decision.

  2. Dear Reuven:

    The whole point of the baseline is that if it is 0.7 ng/ml (who are at notable risk) andf the men with a PSA < 0.7 (who aren't)!

  3. Unless the USPSTF recommendation is modified, mass screenings may just become more popular as insurance companies may not be paying for PSA tests anymore; mass screenings are usually free. This MAY, in effect, result in what USPSTF and most prostate cancer experts don’t want to see: an increase in screening without an informed decision-making process (which will not be available at most mass screening events).

    Screening at 50 makes no sense? I was screened and diagnosed at 65. I am now recurring after salvage radiation, apparently indicating an aggressive cancer. I am still alive after 6 years and I am looking forward to years to come. I am convinced that treatment prolonged my life!

  4. Wolfram:

    If you had had a baseline PSA in your 40s, there’s a much better than even chance you would have known you were at risk, been appropriately diagnosed early, and had curative treatment when it became appropriate (not necessarily immediately). Giving any man a first PSA test when he is 65 is near to useless if he is at risk for clinically significant disease.

  5. When I was 40, nobody knew about the importance of a baseline test at 40, though I did have my first rectal exam at that time. As far as I can trace it back, my first PSA test was at age 47 with a value of 1.3 which today would put me in a higher than average risk category.

    But that is not the point: a 50-year-old man has a life expectancy of about 30 years and a 65-year-old man has a life expectancy of more than 15 years. The point is: an aggressive cancer detected at either age should be [identified to] prolong the patient’s life. Nobody should put numbers on cancer, including PSA value and age, to determine whether or not he should get screened (or treated for that matter). The decision in screening and treatment should include the overall health of the person in question.

    WE ARE NOT NUMBERS, WE ARE HUMAN BEINGS!

    This is wonderfully explained by Dr. Myers in his latest video.

  6. I’m confused when it comes to this magic baseline

    If my father, now 56 years old, has aggressive, metastatic prostate cancer, then if I do a baseline around 40 (or even slightly sooner) and it comes low, example PSA 0.19, will that mean that I am at not much risk or would the genetic profile be the more important factor in determining risk?

  7. Patrick:

    If your father has aggressive, metastatic prostate cancer at 56 years of age, I would certainly consider that your were at significant risk based on family history. Th is might not necessarily be simple genetics; it could have something to do with the environment in which your Dad grew up and lived, his possible exposure to toxic chemicals (e.g., Agent Orange in Vietnam), and other factors.

    While your PSA is down around 0.2 ng/ml, there is no reason for you to think you need to do anything, but if I was you and had a father with metastatic prostate cancer, I would be asking my primary care doctor to check my PSA at least once every two years and maybe once a year, and I would keep a careful record of the dats of the blood draws and the results of those tests over time. Your own personal risk may be no higher than normal, but you would be wise to keep a careful eye on this. I assume that your own doctor does know about your Dad’s condition. Yes?

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