En español | A federal panel of experts is advising that men without symptoms should not be screened for prostate cancer with a common blood test. After decades of being urged to schedule an annual PSA test, this recommendation left men bewildered and many doctors critical.
In its most recent statement, the U.S. Preventive Services Task Force panel concluded that the harms of screening for prostate cancer outweigh the benefits and that screening can lead to unnecessary testing and procedures, such as prostate surgery or radiation therapy. Further, for men 50 to 69, the evidence is convincing that screening does not save lives, the panel noted.
The PSA blood test measures the amount of prostate-specific antigen, a protein produced by the prostate and released into the bloodstream. If prostate cancer develops and grows, PSA levels rise. However, normal results on a PSA test don't always mean that cancer is absent and abnormal results don't always indicate its presence. Infections or benign enlargement of the prostate can also cause elevated PSA levels.
"Like any screening test, a PSA test doesn't make or break the diagnosis of prostate cancer. It simply points to the need for further evaluation," says oncologist Andrew Lee, M.D., of the M.D. Anderson Cancer Center in Houston.
Medicare currently covers one PSA test a year for men age 50 and over.
Pros and cons of screening
The downside of screening is that the test itself can cause problems. Some 70 percent of positive results are false positives — that is, the test mistakenly red-flags the presence of cancer. The only way to tell if it's cancer is a with a prostate-tissue biopsy.
Even if a biopsy shows that prostate cancer is present, the tumor may be so slow-growing and low-risk that it poses no risk to a man's health. Yet a recent study shows that even false-positive results have psychological consequences, including overestimating the likelihood of developing the disease and impaired sexual functioning.
But many physicians are critical of the task force statement. "None of us would dispute that there are harms with screening for prostate cancer, just as there are for screening for any other cancer," says Cleveland Clinic urologist Andrew Stephenson, M.D. "But the task force fails to acknowledge the benefits, which are clear."
The failure of screening is in part due to the limitations of the PSA test itself, notes Stephenson. "The PSA test is good at identifying who has cancer and who doesn't. But it's not good at identifying who has a cancer that should be treated and who has a cancer that won't pose a threat to a man's well-being and survival." The problem is overdiagnosis, which leads to treating a tumor that would never pose a problem.
"Overdiagnosis is harmful if it's linked to treatment," he says. In his practice, half of the men referred to him with a diagnosis of prostate cancer are treated conservatively with "active surveillance" (aka watchful waiting), a strategy of forgoing immediate treatment in favor of regularly scheduled testing and clinical exams to monitor the disease closely.