How often is a PSA test really needed to identify risk?

A re-analysis of data from the Antwerp (Belgium) section of the European Randomized Study of Screening for Prostate Cancer  (ERSPC) has offered us some further insight into the frequency of PSA testing necessary to identify less and more aggressive forms of prostate cancer.

Nelen et al. have compiled data on the number and characteristics of so-called “interval cancers” in men in the screening arm of the Antwerp section of ERSPC who were between 55 and 65 years of age at initial  randomization and who participated in all of the screening rounds they were invited to attend. The total number of men in the screening arm of the Antwerp section was about 1,600. The screening interval in the Antwerp section of the ERSCP  lasted for 6 years on average.

It is important, in understanding this study to appreciate exactly what is meant by an “interval cancer.” The authors defined “interval cancers” as:

  • Cases of prostate cancer diagnosed during the screening interval but not detected by screening and/or
  • Cases of prostate cancer diagnosed as a consequence of a positive screening test if diagnosis through biopsy occurred more than 1 year after that screening test.

Aggressive types of  interval cancers were defined as interval cancers with at least one of the following characteristics:

  • Clinical stage M1 or N1
  • Gleason score of 8 to 10
  • World Health Organisation (WHO) score of 3.

The results of this study can be summarized as follows:

  • The 10-year cumulative incidence of interval cancers was 3.0 percent (n = 50).
  • The cumulative incidence of aggressive interval cancers was 0.5 percent (n = 8).
  • During the first screening interval
    • 36 interval cancers were detected.
    • 20/36 interval cancers (55.6 percent) were detected more than 4 years after the initial screening.
    • 5/36 interval cancers (13.9 percent) were classified as aggressive.
    • All aggressive interval cancers emerged > 4 years after initial screening.

The authors conclude only that the occurrence of interval cancers in this study was higher than in the ERSPC centres that used a shorter screening interval and that aggressive interval cancers started to emerge at least 4 years after initial screening.

We have previously suggested that — at least among men who have no well-defined risk for prostate cancer — PSA testing for risk of prostate cancer may be needed only at 5-year intervals to identify clinically signioficant forms of prostate cancer. It would be inappropriate to suggest that the data from this study specifically supports that suggestion. However, it does at least appear to give some further credence to the hypothesis that an extended period between PSA tests does not place most men at high risk for a diagnosis of clinically significant disease.

We would hope that additional study might be able to clarify whether 3, 4 or 5 years was the most appropriate period between PSA tests necessary to monitor risk in men over 50 years of age with no known risk factors for prostate cancer. We are increasingly convinced that annual PSA tests are unnecessary for the detection of risk among the majority of men of 40+ years of age. Annual testing may, however, be wise for men with known risks for prostate cancer.

5 Responses

  1. I am glad to notice that Sitemaster recommends PSA testing, albeit at a lower frequency than one year.

    It’s also good to note that he recommends yearly testing for those of us who have a family history of prostate cancer, or are African Americans.

  2. Dear Reuven:

    Actually, I was extremely careful not to specifically “recommend” PSA testing or annual PSA testing.

    Please read the final paragraph with great care. It suggests only that if a patient with no known risk wants to monitor his risk, PSA testing is appropriate (but probably doesn’t need to be done every year) and that for men at known risk annual PSA testing may be appropriate.

    We have consistently taken the position that there is currently no other test that is better than the PSA test for monitoring risk of prostate cancer — but that 83.3 percent of American men will never be diagnosed with even low-risk prostate cancer and available screening data provide no compelling support for the value of mass, population-based screening using the PSA test.

  3. “Annual testing may, however, be wise for men with known risks for prostate cancer.”

    As a matter of fact, when my brother was diagnosed with PCa in 1995, I changed my own testing schedule to twice per year and I am convinced that saved my life. I was diagnosed early in 2000 (at age 74+) with aggressive (Gleason 9) prostate cancer. I was treated with IMRT plus hormonal therapy. This year, my oncologist said he considered me cured — his word. My quality of life is good; there are many other ways for a couple to express their love for each other, besides actual sex.

  4. I am a fan of annual screening except where previous PSA results have been extremely low. However, the data in the study regarding incidence provoke the thought that annual screening may be too frequent.

    One reason I believe in annual screening for most men is that there is a much better chance to get a good handle on PSA velocity, especially to document a rise in PSA of more than 2.0 in the year prior to diagnosis, which the D’Amico team’s work and other work indicate is an additional factor indicating aggressiveness (and vice versa for lower PSAVs). Can anyone think of a way to preserve the benefit of knowing the PSA velocity, ideally measured by at least three tests spread over 18 months, while reducing the interval of PSA testing?

    Regarding the very low incidence of aggressive prostate cancer in the study — 0.5%, I’m curious why the researchers used so tight a definition of aggressiveness. It seems it would have been far more useful to include any Gleason 7 cancer rather than just 8 to 10, and any stage 3 cancer, as opposed to just metastatic. Therefore, to me, the study suggests a lower boundary for the incidence of aggressive cancer based on the interval approach used in the study.

    I’m not sure what a WHO score of 3 is. Any explanation?

    Thanks for describing this study to us.

  5. Jim: The WHO score was an older grading method used to assess aggressiveness in the same way as the Gleason score. It was used for years by the Armed Forces Institute of Pathology in the USA and by many non-US pathologists, but as of today it has been almost completely superseded by the Gleason grading methodology.

    With regard to the selection of Gleason 8-10 as opposed top Gleason 7-10, my suspicion is simply that Nelen et al. were making a point that the occurrence of truly aggressive cancers was rare. Gleason 7 cancers are only intermediate risk if there is no other indicator of high risk.

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