Early Promoters Of PSA Screening For Prostate Cancer Do A Turnabout
Posted by medconsumers on February 1, 2005
At first, it appeared to be heresy. A paper published last October in the Journal of Urology indicates that the PSA screening test for prostate cancer has lead to widespread cancer diagnoses in men who did not need to be treated. The paper entitled, “The prostate specific antigen [PSA] era in the U.S. is over for prostate cancer: what happened in the last 20 years?” received surprisingly little publicity. What made it so remarkable was the fact that the lead author, Thomas A Stamey, MD., and colleagues at Stanford University are credited with early promotion of PSA screening in a paper published in 1987. Now, their recent data present a powerful argument against this use in symptomless men.
The paper describes a study that shows the presence of cancer in the prostate increases with age. Autopsies conducted on 525 men, equally divided between white and black men, killed accidentally on the streets of Detroit , showed that 8% of those in their 20s had prostate cancer. There was a linear increase in prostate cancer with each increasing decade of life. About 80% of the men (of both races) who were in their 70s had invasive prostate cancer.
The fact that most prostate cancers will remain dormant is demonstrated aptly by another statistic in this paper: “[Prostate cancer] has an extraordinarily small death rate of 226 per 100,000 men older than 65 years,” wrote Stamey and colleagues. Deaths from prostate cancer are rarer yet in men under age 65, according to the National Cancer Institute. Yet despite these statistics that make a case for not screening symptomless men for prostate cancer, the PSA blood test began to go into widespread use in the late 1980s. There is still no test that can accurately distinguish slow-growing or latent prostate cancer from the type that is moderately rapid and fatal.
Over the course of two decades, Dr. Stamey and colleagues assessed 1,317 consecutive prostates that had been removed surgically between 1983 and 2003—what they called the “PSA era.” The idea was to see how well the PSA test given before surgery accurately reflected the size of the largest cancers. Here’s what they found: “In the first ten years after PSA screening was introduced, there was a reasonably good, although not great, correlation between serum PSA and prostate cancer volume.”
But, as the years went by, things changed completely. When the researchers assessed the prostates removed most recently, that is, between 1998 and 2003, they found that the PSA tests were detecting benign enlargement of the prostate, rather than cancer. Benign prostatic hyperplasia, or enlarged prostate, is a common condition in men over age 60.
Dr. Stamey and colleagues explained their findings in this way: American men between 50 and 80 years have been screened so intensely over the last 20 years that the most significant of the prostate cancers had already been detected. However, they glossed over the substantial harm done to men in the PSA era in terms of unnecessary prostatectomies and unnecessary radiation therapy. The issue was alluded to in only one sentence, using one word— overtreatment.
In a telephone interview, Dr. Stamey said he had no hope that the huge industry that has now built around PSA screening will disappear with his findings. So he stressed the importance of informed consent where it concerns the use of the PSA test in symptomless men. “It is immoral for surgeons not to tell patients that we [men] all get prostate cancer as we age,” said Dr. Stamey, after describing himself as a 76-year-old surgeon who hasn’t had a screening PSA test in several years.
“Patients should be told that there’s a high chance of having prostate cancer that rises with age, but a very low chance of dying of it. Do we really want to screen 100,000 men to save 226 from dying of prostate cancer? In fact, it’s about the same chance of my not driving home safely tonight.” What’s more, he continued, 20 years ago, the prostate was biopsied in only six places, now it’s 36.
What about the PSA test’s possible role in the slight dip in the U.S. prostate cancer death rate? Dr. Stamey gave no credit to PSA screening.
“The death rates from several other common cancers have fallen, too, but we have no idea why.”
Maryann Napoli, Center for Medical Consumers ©