That popping sound you may have heard on Tuesday was made by urologists opening the champagne bottles they had chilled in anticipation of the United States Preventive Services Task Force (USPSTF) upgrading its recommendation about PSA screening for prostate cancer from a D (the harms outweigh the benefits) to a C (it’s an individual decision).
Much like a teacher changing a dissatisfied student’s grade from a D to a C — and only after much complaining — the new guidelines should hardly be construed as a ringing endorsement. PSA screening remains a difficult decision for healthy men and their doctors.
The test measures the amount of a protein called prostate-specific antigen (PSA) in the bloodstream. A PSA level above 4.0 nanograms per milliliter of blood has been used as the traditional cutoff to suggest the possibility of prostate cancer (though experts could easily have picked a 5.0 cutoff many years ago). Screening means testing healthy individuals to see if they might have hidden cancer.
The data on which the USPSTF based its new recommendation for PSA screening is similar to the data it used for its prior recommendation in 2012. No study has shown that the test saves lives or improves the quality of life. It does not reduce mortality or extend survival in any randomized trial to date, nor when all studies are combined together. Let me say that again: There is no proof that PSA screening extends your life, improves the years you have, or reduces your risk of dying.
A large European study showed that the test reduces the risk of dying from prostate cancer by about 20 percent or by 0.11 per 1,000 men per year of follow-up, though this benefit was not seen in all nations. In Finland, for instance, there was no benefit, while there was a larger one in Sweden. Unfortunately, data from this study are not shared with other researchers. That is troubling given recent high-profile reversals with data sharing and reanalysis, including other PSA studies. For matters of public health, it is not OK to keep data secret. We have to put all the cards on the table.
A large American trial of PSA testing, published in 2012, has made its data widely available. This trial showed no benefit from screening but — thanks to data sharing — we know the trial wasn’t perfect. The group assigned to PSA screening was tested appropriately, but some men in the group assigned to no screening had their PSA tested. Why? It was difficult to prevent men in the US from getting a PSA test because, quite frankly, our nation was punch drunk on the test. We were so enthusiastic in those years that it wasn’t possible to do a fair trial in the US. The lesson here is that it is hard to test something in medicine that has already been broadly implemented.
PSA screening still has all the harms we hear so much about: false positives, overdiagnosis — which means treating a cancer that would otherwise not cause harm — and the side effects of diagnosis and treatment, including incontinence, impotence, and even death.
In my mind, the greatest misconception about the test is that we say it “saves lives” when that is uncertain. PSA testing reduces the risk of dying of prostate cancer, but there is no evidence it reduces the risk of dying.
How can we make sense of this difference? A useful analogy is right under our noses: our teeth. Adults have 32 (or 28 if your wisdom teeth are gone), and most of us want to keep every last one.
Prostate cancer accounts for 2 percent to 3 percent of deaths among men, or roughly 1 of 32 deaths. PSA screening isn’t perfect and doesn’t provide any information about other possible causes of death.
PSA screening, then, is like a dentist applying a sealant to one of your 32 teeth, and that sealant reduces the risk of losing the treated tooth by 20 percent.
What about the other teeth? Many experts believe the sealant has no effect — not positive or negative — on the other teeth. Others, including me, believe that the sealant slightly increases the risk of losing one of the untreated teeth, which would offset the small 20 percent benefit for the treated tooth.
Overdiagnosis and overtreatment are common with PSA screening — the USPSTF says it happens in 20 percent to 50 percent of men diagnosed by screening — so even small harms may counteract any benefits of screening. For instance, some treatments for prostate cancer, such as radiation therapy, can increase the risk of getting a second cancer.
Using the teeth analogy, here’s the best-case scenario for PSA screening: It modestly strengthens one tooth. The worst-case scenario: It slightly weakens other teeth.
Despite all of the studies to date, we have no evidence to know which of these two scenarios is true. Instead of being honest about this fact, and letting people decide, the medical profession has brushed it aside and blindly promoted screening based on rhetoric and empty persuasion. Well-meaning celebrities like Ben Stiller haven’t helped.
As an oncologist who cares for cancer patients, I have no desire to trivialize cancer, and I know that prostate cancer is far worse than losing a tooth. So I use the analogy reluctantly, hesitantly, and only because I think it helps us think more clearly about screening. There is a big difference between the phrase “reduces the risk of dying from prostate cancer” and the phrase “reduces the risk of dying.” Men must understand the difference to make an informed choice.
The USPSTF’s C recommendation for PSA screening means the decision should be individualized, something I support. Prostate cancer screening may be OK for some men — those who are more tolerant of risk and uncertainty — but it is surely not right for others. As for African-American men, or men with a family history, the USPSTF provides caution that there is no good evidence to show greater benefit from the test, and it is possible the harms are greater in these groups. PSA screening is OK only if doctors are honest about what the test can and cannot do.
PSA screening has real harms. It reduces the risk of losing one of your 32 teeth by 20 percent, but we have no idea what it does for the other 31 (it may weaken them). For some men, the benefit and uncertainty might be worth it. But for others it may seem like so much for so little.
Vinay Prasad, MD, is assistant professor in the Division of Hematology Oncology at Oregon Health and Science University and the author of “Ending Medical Reversal.” The views expressed in this article are the author’s personal opinions and do not represent those of OHSU.