PSA Testing: The Good, the Bad and the UglyBy
A story about prostate cancer (PC) screening titled “The Great Prostate Mistake” which appeared in the New York Times last week, ”went viral”. Everybody’s talking about it. (See http://www.nytimes.com/2010/03/10/opinion/10Ablin.html?scp=1&sq=ablin&st=cse) I refer to an opinion piece written by Dr. Richard Ablin, a researcher in immunobiology and pathology who invented the prostate-specific antigen (PSA) test in 1970, the most commonly used tool for detecting prostate cancer (PC) today . The test measures the levels of PSA, a protein secreted by cells in the prostate which leaks into the blood, excessively if there is prostate cancer.
Dr. Ablin is clearly unhappy that he released this particular genie from the bottle. He decries the widespread, indiscriminate use of the PSA test, by which he means the practice of testing all men over a certain age regardless of risk. (The recommended age used to be 50, but it was recently lowered to 40 by the American Urological Association). Dr. Ablin believes mass PSA testing has become a ”costly, profit-driven public health disaster”, spurred by greedy drug companies who “peddle” the test and overzealous patient-advocates who sponsor screening events as part of “prostate cancer awareness”.
Dr. Ablin claims the PSA test is hardly better at detecting PC than a coin toss. The test generates a lot of false positives because many common factors other than cancer can cause PSA levels to be elevated. And the PSA test misses 30% of cancers. But by far the biggest problem with the PSA test is that it can’t distinguish between the majority of PCs which are slow-growing and harmless and may not need treatment, and the fast-growing PCs, which require aggressive treatment.
In spite of these limitations, moans Dr. Ablin, doctors have widely embraced the PSA test and used it as a rationale for performing a whole lot of painful biopsies and invasive treatments, most commonly surgery to remove the prostate, radiotherapy and androgen deprivation therapy. These interventions have left hundreds of thousands of men with profound, quality-of-life-diminishing side effects such as impotence and incontinence, for questionable benefit.
Dr. Ablin argues that widespread, routine PSA testing is not worthwhile because PC claims so few lives anyway – only 3% of men who get the disease actually die of it. And any benefit derived from the PSA test is far outweighed by the harm it causes. Dr. Ablin cites a European study which found that to prevent one man from dying of PC, 47 others would have to be treated (surgery is the most popular choice). Somebody likened this to a lottery. One person wins big, very big ,but the other 47 are losers.
I think Dr. Ablin overstates his case. The PSA test is not quite as useless as he makes it out to be. Dr. Ablin acknowledges as much at the conclusion of his article when he urges that men with a family history of PC continue to be tested. But I do agree with the spirit of Dr. Ablin’s argument, that although PSA testing has benefited a lucky few (probably including my own husband), it has been a source of great anguish for many others .
So is it time to dump the PSA test? Not so fast.
To be continued.