Cancer Screening May Be More Popular Than Useful
After decades in which cancer screening was promoted as an unmitigated good, as the best — perhaps only — way for people to protect themselves from the ravages of a frightening disease, a pronounced shift is under way.
Studies suggesting that screening tests like mammograms should be used less do not always find receptive audiences.
Now expert groups are proposing less screening for prostate, breast and cervical cancer and have emphasized that screening comes with harms as well as benefits.
Two years ago, the influential United States Preventive Services Task Force, which evaluates evidence and publishes screening guidelines, said that women in their 40s do not appear to benefit from mammograms and that women ages 50 to 74 should consider having them every two years instead of every year.
This year the group said the widely used P.S.A. screening test for prostate cancer does not save lives and causes enormous harm. It also concluded that most women should have Pap tests for cervical cancer every three years instead of every year.
What changed?
The answer, for the most part, is that more information became available. New clinical trials were completed, as were analyses of other sorts of medical data. Researchers studied the risks and costs of screening more rigorously than ever before.
Two recent clinical trials of prostate cancer screening cast doubt on whether many lives — or any — are saved. And it said that screening often leads to what can be disabling treatments for men whose cancer otherwise would never have harmed them.
A new analysis of mammography concluded that while mammograms find cancer in 138,000 women each year, as many as 120,000 to 134,000 of those women either have cancers that are already lethal or have cancers that grow so slowly they do not need to be treated.
Cancer experts say they cannot ignore a snowballing body of evidence over the past 10 years showing over and over that while early detection through widespread screening can help in some cases, those cases are small in number for most cancers. At the same time, the studies are more clearly defining screening’s harms.
“Screening is always a double-edged sword,” said Dr. Otis Brawley, the chief medical officer of the American Cancer Society. “We need to be more cautious in our advocacy of these screening tests….”