Dr. Patrick Walsh and Dr. Catalona - Two Recent Important Articles
DOES PSA TESTING SAVE LIVES?
A Critical Analysis of Two Randomized Trials
by Patrick C. Walsh, M.D. (reprinted with permission)
Patrick Walsh, MD, John Hopkins University School of Medicine
In March 2009, the results of two long awaited trials were published in the New England Journal of Medicine.1,2 One said that screening with PSA reduced deaths from prostate cancer by up to 27% and the other claimed it didn’t work.
What are we to believe? Like many things "the devil is in the details" and understanding these details could save your life!
First, the positive trial was a landmark study carried out in seven European countries that studied 162,000 men who were randomized to PSA screening every four years versus no screening.1 With long-term follow up out to fourteen years, there was a 20% decrease in deaths from prostate cancer in the group of men assigned to screening. However, since only 85% of these patients actually underwent screening, if one includes only the men who were actually tested, the decrease in prostate cancer deaths is 27%.
This reduction in death from prostate cancer is similar to the 30% reduction in mortality from breast cancer in women who undergo mammography and the 33% reduction in prostate cancer mortality that occurred in the United States between 1994 and 2003 following the introduction of PSA screening. Thus, the results from the European study support other findings and unequivocally demonstrate that PSA testing can save lives.
The second trial, which was carried out in the United States, was half the size of the European trial. It compared screening with PSA every year for six years with no screening thereafter versus no planned screening. It showed no improvement in prostate cancer mortality at 7 years.
In the many sound bites on television and reports in print media proclaiming "no effect", the words "seven years" were conveniently deleted. This is the major flaw in this study. Death from prostate cancer at seven years is meaningless: 1) screening and aggressive treatment are typically reserved for individuals with at least a 10 year life expectancy; 2) any patient who dies within seven years of diagnosis has advanced non-curable disease at the time of diagnosis and would not benefit from PSA screening; and 3) in the positive European trial mentioned above, there was also no improvement in survival at seven years.
The U.S. trial also failed to achieve some of the important milestones that one would expect from a screening trial if it were successful. For example in trials for breast or colon cancer, screening leads to an increase in the number of cases diagnosed and a decrease in the number who are not curable. In the European prostate cancer trial, with screening there was a 71% increase in the number of cases and a 41% decrease in the number of men with incurable disease. For this reason with longer follow up, the favorable impact on mortality is likely to increase. In contrast, in the U.S. study where there was only a 17% increase in the number of new cases and no decrease in advanced disease. For this reason, with longer follow up of the men in the U.S. trial, unfortunately the results will not change.
What’s the problem with the study carried out in the United States? First, it did not test screening versus no screening – it just compared more screening versus a little less screening. In the screening arm, 85% of patients underwent PSA testing compared to 52% in the controls. That’s right, only a 33% difference!
Furthermore, 44% of the men who entered the trial already had 1 or more prior PSA tests. Consequently these men were not only less likely to have cancer, but also less likely to have life-threatening disease. This explains why there were so few cancer deaths in either arm of the study.
Finally, the American study used an outdated cut point for PSA to trigger a biopsy (greater than 4.0 ng/ml versus 3.0 ng/ml in the European trial) and only 30% of the men who developed a PSA greater than 4.0 ng/ml while in the trial actually underwent a biopsy! If most of the men with elevated PSA levels never underwent a biopsy, how can anyone expect this trial to show that screening saves lives!
Why does this study have so many flaws? If they had set out to design a study to discredit PSA testing it would have been difficult to do a better job. However, giving them the benefit of the doubt, maybe they were just trying to simulate what would happen if every man in the United States had a PSA performed but few followed up with a biopsy or treatment. If that were the question, I think we could have already guessed at the answer without spending $110 million.
Granted, it was more difficult to carry out a trial in the U.S. where PSA testing was already well established compared to Europe where random PSA testing was infrequent. However, why didn’t the investigators from the National Cancer Institute admit the shortcomings of their study rather than promote their flawed findings as the Holy Grail? I don’t know why anyone would do this but you can understand where they are coming from by looking at their many interviews on television and in the print media where they state their objections loud and clear.
They believe that the wide-spread use of PSA testing will encourage many men who may never need treatment to suffer unnecessary side effects. In the European study it is estimated that to prevent one prostate cancer death at ten years, 1,400 men would need to be screened and an additional 48 men would need to be treated. Ten years is the earliest time at which one would expect any benefit and if one looks at a 50 year old man who is going to be alive for another 35 years, those odds would be entirely different. Also, with longer follow up in the European trial these odds will improve.
However, if screening for prostate cancer is ever going to receive popular support, it will be necessary to avoid over-diagnosis in men who are unlikely to have a survival benefit (men who are too old or too ill to live longer than ten years) and to avoid over-treatment in men over age 65 who have low volume disease. Most of all, it is imperative for us as physicians to continue to improve the quality of treatments to reduce their morbidity. If one day it were possible to reduce these side effects to a minimum, the debate would end.
What is the take home message? If you are the kind of person who doesn’t wear a seat belt nor goes regularly to the dentist or your family doctor for a check-up and are not worried about dying from prostate cancer, do not undergo PSA testing. On the other hand if you are a healthy man age 55-69 who does not want to die from prostate cancer, the European trial provides conclusive evidence that PSA testing can save your life.
1. European Randomized Study of Screening for Prostate Cancer (ERSPC): Schroder FH, Hugosson J, Roobol MJ, et al. Screening and prostate-cancer mortality in a randomized European study. N Engl J Med 2009;360:1320-8.
2. Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial (PLCO): Andriole GL, Grubb, III RL, Buys SS, et al. Mortality results from a randomized prostate-cancer screening trial. N Engl J Med 2009;360:1310-9.
Dr. Catalona's Position On The Life-Saving Benefits of PSA Screening
The subject of prostate cancer screening continues to draw media attention.
Dr. Catalona believes the coverage is confusing men who are making decisions about PSA screening and early detection for prostate cancer.
His concern is that men, whose lives could be saved by early diagnosis and treatment for prostate cancer, will now find false justification for not screening.
In Quest, he will continue to present his rationale for the life-saving benefits of PSA screening, early detection, and early treatment.
Two Studies: ERSPC and PLCO
The Spring 2009 issue of Quest was devoted to the subject of prostate cancer screening in response to the high interest in the topic created by the publication of two studies in the New England Journal of Medicine. (Articles from that Quest are available on the URF website: www.drcatalona.com)
The European Screening Trial (ERSPC) provides conclusive evidence that PSA screening can save lives; whereas, the United States trial (PLCO) essentially contains no useful information.
Moreover, it is likely that the mortality benefit in ERSPC is an underestimate because of the relatively short follow-up, the relatively long screening interval, the non-use of digital rectal exam as a screening test after the first round, and contamination in the control arm.
In contrast, it is unlikely that the misleading PLCO results will change substantially with further follow-up because the study was fatally flawed from the beginning. The basic flaws included:
- 43% of the study group was prescreened, eliminating high-risk Prostate cancer from the study population.
- 52% of the control population was screened during the study thereby contaminating the actual results.
- No requirement was made for men with abnormal screening results to undergo biopsy and only 40% of those identified did, thus compromising early detection and treatment
- It takes patients about 13 years after recurrence following a radical prostatectomy to die of prostate cancer, but the median follow up for men with cancer in the PLCO was 5-6 years, insufficient to evaluate mortality results and
- Men were included up to age 74 and they are less likely to have a mortality benefit from screening.
Dr. William J. Catalona
I Recommend PSA Screening
I continue to recommend PSA screening to my patients. PSA testing provides the best estimate of risk for having prostate cancer and the greatest chance of avoiding death from this disease.
PSA screening has been widely accepted in the United States and many other countries because it works.
Patients and physicians who are concerned about decreasing the death rate from prostate cancer have relied upon the test because it gives them valuable information and because death rates have continued to fall during the PSA era.
Although the PSA test is not perfect, it is effective in identifying men at high risk for prostate cancer and for detecting it early. Moreover, a strong correlation exists between PSA and aggressive forms of the disease.
Decrease in Advanced Stage Diagnosis
During the PSA screening era in the U.S., there has been an 85% decrease in the percentage of prostate cancer cases that present with advanced-stage disease and a 40% reduction in the age-specific prostate cancer mortality rate.
Similar trends have been reported from the World Health Organization Database in countries that have adopted PSA screening but not in those that have not. These impressive trends would not have occurred if screening detected only harmless cancers.
Screening Makes Treatment More Effective
Early detection would be useless without effective treatment.
The most effective curative treatment, radical prostatectomy, was available before the PSA era, but this treatment didn't show falling death rates until PSA testing was implemented.
Curative treatments are effective mainly in patients with early disease, which is why the most important factor responsible for the falling death rates is PSA screening.
Dr. Catalona's research group participates in large prostate cancer screening events whenever possible.
Cure Is the Goal
The physician's job is to ensure that patients receive effective, high-quality treatment to maximize cure rates and minimize side effects.
Goal of Screening
The goal of screening is to detect cancers that could cause suffering and death, but screening may also detect cancers that would never cause symptoms. Currently, because of limited ability to distinguish between harmless and lethal cancers, most cancers are treated.
Over-diagnosis Is Minimal and Inevitable
Some "over-diagnosis" and "overtreatment" will occur with early detection screening, but research on my 5,000+ patients shows it is minimal compared to the "underdiagnosis" of prostate cancer.
To date, no validated test is superior to PSA as a screening device. There is always hope that the PSA test, itself, may be further refined or some other test discovered that would be even more precise. The intelligent use of such tests could certainly diminish, but never completely eliminate, some over-diagnosis and over-treatment.
Presently, no one is able to predict the aggressive or non-aggressive traits of diagnosed prostate cancer. Which patients or doctors would choose to play a game of Russian Roulette with the diagnosis of prostate cancer when so many men die from it?
Letter From Patrick C. Walsh, MD*
Prostate Cancer Testing Is Best Option for Men
Until an alternative exists, prostate cancer testing is the best option we have to allow men to make an informed decision. Disparaging testing does a great disservice. Because prostate cancer produces no symptoms until it's too far advanced to cure, as appropriate, men should have a PSA test and examination.
In 1990, before PSA testing, only 68% of newly diagnosed men had localized cancer and 21% were metastatic.
Today, 91% are diagnosed with localized disease and only 4% have metastases.
With the ability to diagnose cancer earlier and treatment advances, U.S. deaths from prostate cancer have fallen 40% in ten years, a greater decline than for any other cancer.
Today, men have a choice that once did not exist: Undergo testing and, if there is cancer, make an informed choice for treatment or observation, or do nothing and run the risk of a diagnosis until it's too late.
I choose to know.
*Patrick C. Walsh, M.D. is the University Distinguished Service Professor of Urology at the James Buchanan Brady Urological Institute, Johns Hopkins Medical Institutions
Under-diagnosis Needs More Attention
"Under-diagnosis" and "under-treatment" are important concerns that have received much less attention than "overdiagnosis" even though they have life-threatening consequences.
"Under-diagnosis" and "under-treatment" occur when prostate cancer is not detected until it has spread beyond the prostate and when that unnecessary delay in treatment prevents a cure that would have been the result of earlier treatment.
Research on my 5,000+ patients shows "underdiagnosis" is more of a concern than "over-diagnosis."
Concern Over Active Surveillance
Active surveillance and focal therapy have emerged as strategies to guard against over-treatment; however, physicians should be careful not to throw out the baby with the bath water.
With active surveillance (also known as "watchful waiting") or focal therapy (also known as "the male lumpectomy"), potentially life-saving treatment may be delayed in patients with initially under-graded or understaged tumors. Some will slip through the cracks and have unnecessary suffering and death from prostate cancer.