Despite the evidence, PSA testing sparks controversy
By Deborah Gesensway
TORONTO—After more than 20 years of research and debate, including the recent publication of two large case-control studies, the question of whether or not to regularly screen men for prostate cancer using PSA testing remains a conundrum.
Authors of those two studies faced off against one another during a special Sydenham Society debate on the “PSA Conundrum” at this spring’s Society of General Internal Medicine (SGIM) annual meeting. The only point of agreement during the debate was that the prostate-specific antigen (PSA) test is a poor screening test for prostate cancer.
One of the studies, conducted at 10 VA medical centers and published in the Jan. 9, 2006 issue of Archives of Internal Medicine, did not find that PSA screening reduces mortality. The other, published in the August 2005 issue of the Journal of Urology, found that PSA screening of asymptomatic men is “associated with a significantly reduced risk of metastatic prostate cancer.”
“PSA is not a great test,” said Neil Fleshner, MD, head of the division of urology at the University of Toronto and one of the authors of the study published in the Journal of Urology. “But here is why we need to use PSA: Before PSA, we found men way too late.”
PSA screening itself may not be a good marker for prostate cancer—instead, it’s an indication of benign changes like hyperplasia, he explained. But picking up a rise in a man’s PSA level is the incentive for men to have a biopsy, which can detect prostate cancer that is serious enough to warrant treatment.
“PSA is not a great test, but a reason to do a biopsy is,” Dr. Fleshner said.
On the other side of the debate was John Concato, MD, associate professor of medicine and director of the Clinical Epidemiology Research Center at the VA Connecticut HealthCare System, and a co-author of the Archives of Internal Medicine article. He argued that verbal informed consent should be obtained from patients before using PSA as a screening tool, because evidence of improved survival is lacking.
The potential harm of widespread screening of asymptomatic men without risk factors may outweigh benefits for certain patients, Dr. Concato said. Possible harms include overdiagnosis of indolent disease and subsequent unnecessary treatment, which carries a substantial risk of urinary incontinence and sexual dysfunction.
Dr. Fleshner countered that the tremendous potential for overdetection isn’t necessarily bad, given that prostate cancer is the most common malignancy in men. “What is potentially bad is the treatment,” he said. As experts come to understand more about the natural history of prostate cancer, consensus is emerging that a watchful waiting approach is more appropriate than aggressive treatment for many low-grade and slow growing prostate cancers.
According to the National Cancer Institute, only 25%-30% of men who have a biopsy due to an elevated PSA level actually have prostate cancer. On the other hand, many small tumors are very slow-growing and are unlikely to shorten a man’s life.
“The smarter thing would be to find more and treat less,” Dr. Fleshner said.
But, said Dr. Concato, that strategy just isn’t realistic in our society, adding that it is bold to say one can find a tumor and then not treat it. Decisions in cancer are often based on fear.
Analysts of the two studies have written that there are enough methodological differences between the two trials to explain the differing results. Dr. Fleshner suggested that the Archives of Internal Medicine study might have come to the same conclusion as the Journal of Urology study if the former had a longer follow-up period. Critics of the Journal of Urology study, however, contend that measuring cases of metastatic disease, rather than mortality, is less useful because men diagnosed with metastatic prostate cancer may die of other causes.
Many are awaiting the results of a multiyear trial by the National Cancer Institute and other medical organizations called the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial. PSA experts at the conference pointed out, however, that enrolling patients in a randomized controlled trial where some patients forego screening will be difficult because of the widespread acceptance of PSA screening.
The debate likely will continue until research, currently underway, determines ways of distinguishing between slow-growing and fast-growing cancerous and noncancerous conditions.
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