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No, a federal task force didn't 'change its mind' on the use of the PSA test for prostate cancer screening

PSA test for prostate cancer screening
REUTERS/Michaela Rehle
The panel still recommends against PSA-screening for men aged 70 or older.

In 2012, the U.S. Preventive Services Task Force (USPSTF) recommended — amid much controversy — that men not be routinely given the PSA (prostate-specific antigen) blood test for prostate cancer screening. The test’s clear potential for harms outweighed its small potential for benefit, they said.

Earlier this week, the task force has updated that advice: The PSA test should still not be used routinely, they say, but physicians should discuss its harms and benefits with men aged 55 to 69. Each man can then “incorporate his values and preferences into his decision” about whether or not he wants to be screened. 

The panel still recommends against PSA-screening for men aged 70 or older.

The draft recommendations (they will not be finalized until later in the year) apply to adult men at average or increased risk for prostate cancer who have not been diagnosed with the disease and have no signs or symptoms.

‘A wrong impression’

In the days since that update was published, some media headlines have made it seem as if the USPSTF has “changed its mind” or is now “OK” with PSA-screening.  But, as Kathlyn Stone, an associate editor with the Minnesota-based HealthNewsReview points out, “that would be the wrong impression.” Here’s why:

What the revised guideline does is make a slight change. It changes the recommendation for routine prostate cancer screening from a “D” (which discourages the service since “There is moderate or high certainty that the service has no net benefit or that the harms outweigh the benefits.”) to a “C (which means that physicians should “Offer or provide this service for selected patients depending on individual circumstances,” and that “There is at least moderate certainty that the net benefit is small.”) 

“The main point,” adds Stone, “is that men who are candidates for testing (ages 55 to 69) should discuss the benefits and harms of the test with their doctors and make a personal decision about whether to take it.”

‘Hardly a ringing endorsement’

Dr. Vinay Prasad, an oncologist at Oregon Health and Science University, agrees. “The new guidelines should hardly be construed as a ringing endorsement,” he writes in a commentary for STAT. “PSA screening remains a difficult decision for healthy men and their doctors.”

“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,” he explains. “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.” 

The potential harms are numerous: “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,” says Prasad.

“In my mind, the greatest misconception about the test is that we say it ‘saves lives’ when that is uncertain," he adds. "PSA testing reduces the risk of dying of prostate cancer, but there is no evidence it reduces the risk of dying.”

Understanding all options

As Dr. Otis Brawley, chief medical and scientific officer with the American Cancer Society, points out in a commentary for CNN, “it is fair to say the harms of prostate screening are better proven than the benefits, although benefits likely do exist.”

“One proven harm is overdiagnosis,” he notes. “Some cancers, ironically the ones easiest to diagnose and cure, are so slow-growing they are of no threat to the patient: They do not need to be cured, as they would never do harm if left alone. One epidemiologic study suggests that more than 1 million American men received unnecessary treatment over the past 25 years.”

Brawley applauds the idea of shared patient-doctor decision-making regarding PSA screening. “Good scientific research has bought about improved understanding of cancer and the limitations of screening tests, diagnostics and treatment,” he says. “This is leading more and more to professional guidelines that respect patient preference and put the screening decision in the hands of the patient.”

Brawley also hopes, however, that men diagnosed with prostate cancer are not rushed into treatment, but given a chance to “explore and consider all reasonable options.”

“Recent studies of health practices show a movement away from immediate aggressive therapy for all prostate cancers and increasing use of ‘active surveillance’ or monitoring when PSA testing finds a low-risk cancer,” he points out. “That means fewer harms from surgery and radiation.”

A key factor

The greater acceptance of active surveillance as a treatment strategy seems to have been a key factor behind the USPSTF’s updated recommendation.

“In 2012, we were … very concerned about the harms [of screening] and the harms of overtreatment,” said the chair of the task force, Dr. Kirstin Bibbins-Domingo of the University of California, San Francisco, in an interview with Clinical Oncology News. “There are now strategies that can help some men mitigate the harms that may be associated along the way with prostate cancer screening and treatment.”

In addition, she said, active surveillance “appears to be effective; it is gaining increased use in the U.S., from 10% to now 40% among low-risk men, and this strategy means that some men with low-risk prostate cancer can avoid treatment altogether, and other men at least will be able to delay treatment.”

But, as Prasad cautions in his STAT commentary, “PSA screening is OK only if doctors are honest about what the test can and cannot do.”

“For some men, the benefit and uncertainty might be worth it,” he adds. “But for others it may seem like so much for so little.”

FMI: You can read the USPSTF’s report on its updated recommendations on the panel’s website. The draft recommendations are open for public comment through May 8.

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Comments (4)

Overall death rates

It is scientifically inappropriate for your article to cite arguments that PSA screening has not been shown to reduce overall death rates. Here is the reason for that: given that many men in this age range die of natural causes over a 10 or 15 year period, you would need unrealistically high sample sizes in a randomized control trial to find the expected effects on overall death rates. If you do a power analysis, you would need a RCT of PSA screening with 4 or 5 million men to detect effects on overall death rates of the expected size.

In contrast, effects on prostate cancer death rates are statistically easier to detect because deaths from prostate cancer are rarer events, and hence a change in such rates stands out more. In fact, both the European and American PSA screening experiments picked their sample sizes so that they had adequate power to detect effects on prostate cancer deaths. Neither study was ever intended to provide useful information on overall death rate effects.

Therefore, it is true to state that there is no evidence that PSA screening reduces overall death rates, but only if you immediately note that no study has been done with an adequate sample size to detect such effects, and that no study will probably ever be done, given the ridiculously large sample sizes that would be required.

In fact, in the European study, the overall death rates in the treatment group (the screened group) were lower than in the control group. The difference was about twice the magnitude of the decline in the prostate cancer death rate. But the statistical imprecision in estimated effects on the overall death rate are much higher, so one can't reject a very wide range of death rate effects.

I also think your coverage of this topic could be made more balanced by talking to Dr. Ruth Etzioni of the Fred Hutchinson Cancer Center in the state of Washington, who has done several simulation studies suggesting that SMART prostate cancer screening strategies (e.g., screening every two or three years rather than every year, using active surveillance more if biopsy is positive, etc. ) can mean that PSA screening is a more sensible strategy. Her work is extensively cited in the more recent USPSTF work, and I think influenced their revised recommendation.

Fundamentally, it comes down to this: PSA screening probably saves lives, but even the smartest screening and treatment strategy probably has a ratio of at least 4 or 5 men who become impotent from the treatment but who would not have died from prostate cancer, to 1 man who as a result of screening and treatment did not die from prostate cancer. The reason the screening strategy should be individualized is that different men would view this information differently. Are you willing to reduce your risk of death by x% at a cost of increasing your risk of impotenece by 5 times x%? Some men would say Yes, others No.

What is the benefit?

"Dr. Otis Brawley, chief medical and scientific officer with the American Cancer Society, points out in a commentary for CNN, “it is fair to say the harms of prostate screening are better proven than the benefits, although benefits likely do exist.”"

Dr. Brawley does not know that significant benefits likely do exist. The best he can say is that it is possible that a small prostate cancer survival benefit exists that is too small to detect anywhere except in RCTs in 2 countries, Sweden and The Netherlands. The Swedish result is particularly strange because it is statistically significantly different from the European average.

"But, as Prasad cautions in his STAT commentary, “PSA screening is OK only if doctors are honest about what the test can and cannot do.”"

Unfortunately, the vast majority of doctors are not honest about what the test can and cannot do and never have been. There are still 69% of doctors who either don't tell their patients anything significant about the PSA screening they are getting or only tell them about the "benefits": www.doctorslounge.com/index.php/news/pb/71357

"If you do a power analysis, you would need a RCT of PSA screening with 4 or 5 million men to detect effects on overall death rates of the expected size."

Unfortunately, inability to prove benefit is still a failure to prove benefit. Unless there is an improvement in overall survival, there is no proof of benefit to justify the proven harms: www.bmj.com/content/352/bmj.h6080

Your last comment seems hard to defend

You say the following in response to my comment:

"""If you do a power analysis, you would need a RCT of PSA screening with 4 or 5 million men to detect effects on overall death rates of the expected size."

Unfortunately, inability to prove benefit is still a failure to prove benefit. Unless there is an improvement in overall survival, there is no proof of benefit to justify the proven harms: www.bmj.com/content/352/bmj.h6080 "

Therefore, my understanding of your position is as follows:

All proposed treatments are guilty until proven innocent.
If it is impossible to do a definitive study to show a statistically significant benefit for overall survival, then one should never recommend that treatment if it has any harms.

I think that position is hard to defend, and goes against common sense.

Statistical significance is meant to be a tool to aid decision-making, not a way to reject anything that is not statistically significant.

My assertion is that there is no statistically significant evidence that the overall death rate reduction due to prostate cancer screening differs from the reduction in the prostate cancer death rate. Can you refute that assertion? I don't think you can, because you don't have a study with 5 million participants.

Of course, we also can't refute the proposition that the effect of screening on overall death rates is zero, because again we don't have the 5 million subject RCT.

Your position apparently is that we should never do PSA screening for the next million years of human history, because we are highly unlikely to ever do a RCT with a large enough sample size. That is hard to defend.

I was never given the option, and now have a death sentence

After age 52 my large HMO stopped giving me routine PSA tests, and never said one word about them.

At age 65 I was admitted to an ER in great pain, with incurable Stage IV Prostate Cancer and a PSA of 5,006 (compared to normal range of 1-4) that had already spread to numerous bones and lymph nodes. I never had the options of early detection, active surveillance, or early curative treatments.

Over the next few years I will experience even worse side effects (including eventual death), and incur far greater cost burdens on the Medicare and secondary insurance systems, to say nothing of profound impacts to my family.