I learned a new word this week: pseudoepidemic. That’s what happens when people start looking really hard for a disease that didn’t get much attention earlier, and then–not surprisingly–the disease suddenly becomes much more prevalent.
This is precisely what happened with prostate cancer in the early 1990s, just after screening tests for prostate-specific antigen (PSA) became widely available. As explained by NIH’s Paul Pinsky and colleagues in an article in the New England Journal of Medicine this week, prostate cancer rates rose from 135 (cases per year, per 100,000 men) in 1988 to 220 in 1992, a 63% increase in just four years. Rates slowly dropped after that, but they remained above 150 through 2009.
No one believes that this increase represented an actual increase in the rate of prostate cancer. Instead, it was an increase in the rate of diagnosis, made possible by the PSA test. After this simple blood test became available, millions of men started getting routine PSA testing. The idea was that, because prostate cancer increases the levels of PSA in the blood, this test could detect cancer early, which in turn would save lives.
It hasn’t worked out that way. The problem is that, as a large body of evidence has now shown, most prostate cancers are slow-growing, “indolent” tumors that don’t kill you, at least not before something else does.
What’s worse is that the treatments for prostate cancer have very serious, life-altering side effects. 20-30% of men treated with surgery and radiation suffer from long-term incontinence, erectile dysfunction or both.
This is especially problematic given that the false-positive rate of PSA testing is as high as 80%. In other words, if your doctor tells you that your test was positive, there’s an 80% chance that you don’t have cancer. Many men, though, elect for further, much more invasive testing after a positive result, because who can sleep at night without knowing for certain?
But how about the benefits of early detection? Alas, they did not materialize. Very large trials (including the PLCO study, with over 75,000 participants) showed that routine PSA screening did not prevent any deaths. The only study to show any benefit, ERSPC, had serious flaws, as explained by Ian Haines and George Miklos in the Journal of the National Cancer Institute.