Forgoing a test to detect prostate cancer could mean that three times as many men would fail to have the disease detected before it spreads to other organs, according to a paper in Cancer on July 30. This new finding arrives just months after the U.S. Preventative Service Task Force issued a recommendation against using PSA screening. The task force gave PSA screening a grade of "D," meaning it does more harm than good for most men.

The FDA approved PSA screening in 1986 as a diagnostic test to detect prostate cancer, and it has been controversial from the beginning. The screening has a high false positive rate because PSA levels rise from nonmalignant prostate growth. Additionally, many prostate cancers grow so slowly that they will never cause problems, and it is nearly impossible to tell which cancers need to be treated and which can be left alone.

Surgery or radiation used in treatment can produce incontinence or impotence. As with any surgery, there is a small risk of death or other serious complications, and it's painful, even under the best of circumstances. The task force analyzed several large studies and determined that the benefits of screening and treatment did not outweigh the risks.

The goal of the Cancer study was to determine how many cases of prostate cancer might be missed until they metastasized if PSA testing were eliminated. Metastatic prostate cancer, a malignancy that has spread to distant organs, is usually symptomatic, leading men to seek treatment. It's generally fatal within a few years. Researchers analyzed data from the Surveillance, Epidemiology, and End Results (SEER) Program to determine the prevalence of men who were diagnosed with metastatic prostate cancer as their initial prostate cancer diagnosis, rather than a less invasive form.

The researchers used data from 1983 to 1985, the three years immediately preceding the PSA screening test, to determine the rate of metastatic prostate cancer cases without screening and used the rate to extrapolate the number of cases in 2008, the latest year for which data are available.

They then compared the expected rates to the actual rates for that year and calculated that approximately 25,000 men would have been given an initial diagnosis of metastatic prostate cancer in 2008 without screening, as opposed to the approximately 8,000 who did.

Edward Messing, the senior author of the study, says that PSA is capable of detecting the disease earlier, which could, in theory lead to fewer deaths from prostate cancer. Marc Garnick, a prostate cancer expert at Harvard Medical School, points out, "this would have been a much more powerful study if they had mortality outcomes, not the incidence of metastatic disease."

In fact, Garnick says the clinical trials that have addressed mortality rates have already been done, and they indicate no difference in overall survival or prostate cancer survival in men who underwent screening. Studies like Messing's, he says, are trying to poke holes in the research. "Every single time these studies come out, the backlash is that the studies were flawed. I'm not aware of any program in medicine where randomized studies posed in prestigious journals come out with these negative conclusions, and everyone is trying to data mine the conclusions. It's unprecedented."

Garnick says that PSA screening is based on the faulty assumption that cancer starts small, becomes localized in the prostate, advances to nearby regions of the body, becomes metastatic, and then kills. If this were the case, screening studies should have showed that more lives were saved. "The screening studies show that there's no difference in mortality. The biology of the cancer trumps the stage of the cancer."

2 Comments

1. 1. Tugboat1329 09:55 PM 8/3/12

   In the first place, the Preventive Services Task Force as a group does not have any special expertise in the area of prostate cancer. Not one member is either a urologist or an oncologist. In fact, three of them are pediatricians and two are specialists in women's health issues. Where is their expertise in urologic oncology?
   
   It is not "nearly impossible" to tell which cancers definitely need to be treated. When the pathologist examines the biopsy material, he/she assigns it a Gleason score. This is a measure of how much the cellular architecture departs from normal. The maximum abnormal appearance gets a Gleason 10 score - this is highest in aggressiveness, which requires some form of treatment or death is highly likely in a couple of years.
   
   It is not a faulty assumption that the cancer starts out localized to the prostate and then spreads. I was diagnosed with PCa (Gleason 9) in April 2004. The only warning I had was a rapidly rising PSA value. Available imaging techniques at that time detected the cancer within my prostate and did not detect any metastases. I was treated with external radiation focussed on the gland and nearby lymph nodes. I was also put on hormone suppression therapy until October 2006. Since then, to date, my PSA has been low and steady at 0.20 or less. I have a personal background in biomedical research (including a cancer project) in connection with earning a doctorate in microbiology. I am not aware of any form of cancer that springs up full-blown all over the place.
   
   My situation also greatly weakens the assertion that the cancer had already metastasized at the time of first diagnosis. It has now been about six years since I had any form of treatment. If there were any viable cancer cells left, wouldn't they have revealed themselves by now?
   
   Manuel Rosenbaum

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2. 2. ssm1959 07:25 PM 8/7/12

   Fully agree with the comments above. Modeling studies may suggest how averages perform but they are very poor predictors for individual patients. When applied to the patient care setting the result is over treatment of some and gross under treatment of many. When institutional rules are implemented based on such reports they become a self fulfilling prophecy thus stifling investigation into a better understanding of disease mechanisms and treatment.
   
   The only message to take from this is that we do not know enough about this disease yet. The PSA was our first best attempt at as screening tool. With better understanding of the etiology and pathogenesis we will find ways to separate the slow lesions that will not be aggressive from those that need intervention. As we go through this process treatment will become focused on those individuals needing it and costs will drop.
   
   As our healthcare system administrators become incentivized to find excuses to not treat the elderly we will see more recommendations like those from the Preventative Services Task Force. The result will be the abandonment of many patients who are in good health and could live many more quality years if therapy was avialable but it will not, at least within these shores. Not to worry though, many surgeons are already prepping satellite clinics in Costa Rica where they can treat their patients denied by our evolving system. So if you can afford it you can be treated. Isn't that the "two tiered system" that our representatives were trying to avoid?

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