The humble little PSA test has become a hot-button ethical issue.
The PSA (prostate-specific antigen) test is a blood test that can detect prostate cancer at an earlier stage than can physical exam. It is not a perfect test; it misses about 25% of cancers. But it is the best thing we have for detecting prostate cancer early.
The United States Preventive Services Task Force (USPSTF) reviews all of the available evidence regarding screening tests for various conditions, and makes recommendations based on the scientific evidence. Earlier this month, the USPSTF posted a draft of its update to its 2008 prostate cancer screening guidelines. The earlier guidelines had recommended that men over 75 not be screened with a PSA test, and said that there wasn’t enough evidence to make a recommendation one way or the other for younger men. The proposed new guidelines, based on more recent studies, go further, giving screening a “D” recommendation, which means that there is moderate or high certainty that the service has no net benefit, or that the harms outweigh the benefits, and the task force discourages use of the service.
But how can a PSA cause harm? It’s just a poke in the arm, right?
It is not the test itself that causes harm, but what we do with it. 90% of men with PSA-detected prostate cancer undergo radiation and/or surgical treatments that have considerable risks and side effects. The chair of the USPSTF said that for every 1,000 men treated for prostate cancer, five die of perioperative complications; 10-70 suffer significant complications but survive; and 200-300 suffer long-term problems, including urinary incontinence, impotence or both.
These numbers might be acceptable if there were evidence that treating early prostate cancer did some good. But, counterintuitive as it may seem, studies have shown little if any positive benefit from treating prostate cancer early. When men diagnosed and treated by PSA screening are compared with those who are not treated, there is virtually no reduction in prostate cancer mortality at 10 years.
J. A. Muir Gray wrote, “All screening programmes do harm; some do good as well.”
For a profession that takes seriously Primum non nocere, “FIrst, do no harm,” it seems, with what we know at the present time, that this particular screening test may contravene our first ethical principle.