U.S. task force: End routine prostate cancer screening
CONFLICTING STUDIES
The task force analyzed 64 studies, but focused on two, both published in 2009 and updated this year.
The U.S. study compared 76,685 men aged 55 to 74. About half were assigned to receive annual PSA screening and half to “usual care,” which sometimes included a PSA test. The study found no evidence that PSA screening saved lives after 13 years.
The European study was similar, with about half of 162,243 men aged 55 to 69 getting regular PSA tests and half not. But for every 1,055 men who were screened every one to four years, there was one fewer death from prostate cancer after 11 years compared to men in the unscreened group. That is the basis for the task force’s conclusion that PSA screening for a decade will prevent at most one man in 1,000 from dying of prostate cancer.
The trials themselves were imperfect, polarizing the debate even further.
The American trial was marred by the fact that some men in the “unscreened, usual care” group did receive PSA tests. Such so-called crossovers can weaken a trial’s conclusions.
“With the rate of screening in the ‘unscreened arm’ matching that in the ‘screened’ arm, you can never measure a difference” in the death rates “even if one exists,” said D’Amico.
The trial scientists disagreed, saying the crossovers were statistically equivalent to having fewer people in the trial, said biostatistician Paul Pinsky of the National Cancer Institute, a member of the study team. “But there was twice as much screening in the intervention arm, and we did not find a mortality benefit.”
The European study is actually seven studies, each from one country. In five, the results mimicked the American findings: no statistically significant reduction in deaths from prostate cancer among screened men. But studies from Sweden and the Netherlands showed benefits.
The European scientists and their supporters argued that the Swedish trial in particular was strong enough to stand on its own as evidence that PSA screening saves lives.
Perhaps the greatest problem with the European study is that the screened men diagnosed with prostate cancer generally received top-of-the-line care from academic physicians. If the unscreened men developed prostate cancer, they received less specialized, less aggressive care. “That means this was a trial not only of PSA screening but also of aggressive vs. non-aggressive treatment,” said Brawley.
WEIGHING HARMS
Against the tiny benefit of PSA testing, the task force weighed its harms. At least 15 percent of PSA tests will trigger a biopsy, after which up to one-third of men experience pain, fever, bleeding, infection, difficulty urinating, or other problems requiring medical attention, studies show.
As many as 1 in 6 American men will develop prostate cancer during their lifetimes. Prostate cancer is the most frequently diagnosed cancer in males and the second leading cause of cancer death, after lung cancer. Most cases are diagnosed in men 65 years of age or older. Some prostate cancers progress quickly and cause death within months or a few years, but most grow slowly and never pose a serious threat. Prostate cancer screening tests are an important subject for men to discuss with their health care providers.
Expert panels have reached different conclusions about recommending universal screening for prostate cancer. Many complicated issues are involved:
- Side effects of treatment (impotence and incontinence) can be more harmful than the cancer itself (about 1 in 4 cancers is slow-growing and may not cause any trouble).
- Current technology cannot tell a slow-growing cancer from a fast one, and a man’s health or life expectancy may never be affected by the cancer.
- Tests for prostate cancer do not detect all cases, and about one third of positive results do not prove to be cancer.
Some groups urge testing because the majority of evidence, though not conclusive, shows that early detection of prostate cancer saves lives. Since the introduction of blood tests for prostate-specific antigen (PSA tests) in 1990, more prostate cancers are being caught before they spread to other organs and become difficult to cure. However, the experts do not have enough information to conclude that this is a direct “cause and effect” relationship.
If a biopsy finds seemingly malignant cells, as happens to 120 in 1,000 screened men, about 90 percent of men opt for surgery, radiation or hormone-deprivation therapy. Up to five men in 1,000 opting for surgery will die within a month of the operation; 10 to 70 more will have serious cardiovascular complications such as a stroke or heart attack.
After radiotherapy and surgery, 200 to 300 of 1,000 men suffer incontinence, impotence or both. Hormone-deprivation therapy causes erectile dysfunction in about 400 of 1,000 men.
“When you stack up those harms, the tiny or zero benefits do not outweigh the risk,” said task force co-chair Dr. Michael LeFevre of the University of Missouri Medical School. Because PSA tests cannot distinguish between aggressive and indolent cancer, said ACS’s Brawley, “men are rendered impotent and put in diapers, and for what?” he asked. “They never really had cancer in the first place.”
The task force is not saying no man of any age under any circumstances should undergo PSA screening. “A D recommendation does not preclude discussions between clinicians and patients to promote informed decision making that supports personal values and preferences,” it said. The recommendation is against routine screening.
“Our recommendation should not preclude a physician offering a PSA test or a man requesting it,” said co-chair LeFevre. He would be glad to provide the test for his patients, he said, if the decision were based on a clear understanding of the possible benefits and harms. ACS’s Brawley agrees that “a fully-informed man who wants to be screened in his doctor’s office should be screened.” Only if physicians are prepared to explain all this, including that PSA screening misses just as many cancers as it finds, said the task force, can men make an informed choice.
Experts on both sides do agree that mass free screenings offered by hundreds of urology clinics and hospitals should end. “There is minimal discussion of risks and benefits; a pamphlet isn’t going to do it,” said D’Amico. “But a lot of fear gets invoked.”
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By Sharon Begley
NEW YORK