Is PSA testing obsolete? An annual test for prostate specific antigen (PSA) has now become a ritual for
many men over the age of 50 years. The aim of the test is to obtain an early warning of prostate cancer;
however, elevated PSA values are also closely associated with the size (weight) of the prostate itself as well
as with the presence of prostatitis (prostate inflammation) and benign prostatic hyperplasia (prostate
enlargement).
The PSA test was developed and validated by Dr. Thomas Stamey and colleagues at Stanford University in
the early 1980s and was hailed as a great breakthrough in the fight against prostate cancer. In 1989 this
group confirmed that PSA level was directly proportional to increasing clinical stages of prostate cancer. In
October 2004 Dr. Stamey and his group declared that, "The prostate specific antigen era in the United
States is over for prostate cancer." What happened?
The Stanford team examined 1317 prostates removed during radical prostatectomy during four 5-year periods between August 1983 and July 2003. They compared PSA values obtained prior to prostate removal with actual information about the size and aggressiveness (Gleason score) of the largest cancer in the prostate. During the first period (1983-1988) there was excellent correlation between preoperative PSA levels and cancer severity parameters such as the volume of the largest cancer, capsular penetration, positive lymph nodes, percentage seminal vesicle invasion, percentage of largest cancer with a 4/5 Gleason score, and prostate weight. During the period 1999-2003 there was no correlation whatsoever between preoperative PSA values and any of the above parameters, except the weight of the prostate. In other words, during the 20-year period of the study the PSA test has been reduced from being a significant predictor of cancer to being solely a predictor of prostate weight. The researchers conclude that, "PSA today as a basis for diagnosing and treating prostate cancer is related only to the amount of benign prostatic hyperplasia in the prostate."
The problem, of course, is that men are now being so intensely screened that an inordinately large number
of prostate cancers are diagnosed and treated even though they were unlikely to ever cause a problem. It is
estimated that 8% of men in their 20s and 80% of men in their 70s have invasive prostate cancer and yet
only 0.2% over the age of 65 years actually die from it. The researchers also comment on recent
suggestions by urologists to lower the cut-off point at which a biopsy is performed from 4.1 to 2.6 ng/mL
stating that this would simply "compound the tragedy" by adding millions of men to the biopsy list.
The researchers conclude that the era in which a PSA test was a valid marker for prostate cancer is
probably over. However, the test will continue to be useful as a marker for benign prostatic hyperplasia and
as a tool for measuring the success, or otherwise, of radical prostatectomy and radiation. They also
conclude that a new serum marker, which is truly indicative of serious prostate cancer, is urgently
needed. |
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