Catch cancers early and treat them before they become deadly. That’s the idea behind cancer screening, and that’s clearly how it works with pap smears for cervical cancer and colonoscopy for colon cancer.
But in some cases screening can lead to aggressive treatment of slow-growing tumors that would never have caused a problem if left alone — and the treatment itself can carry serious side effects. Screening also doesn’t help if fast-growing cancers crop up after one screening and spread rapidly to become nearly untreatable before the patient’s next screening.
As we’ve pointed out before, the jury is still out on PSA testing for prostate cancer, a disease that is deadly for some men but slow-growing and harmless for many others. A U.S. study of 77,000 men aged 55 to 74 who have been followed for seven to 10 years has yet to show any benefit from PSA testing, researchers reported earlier this year. A separate analysis of data from Europe found that PSA testing did save lives, but that for every life it saved, 47 men were treated unnecessarily.
The evidence suggests that mammograms for women over 40 do save lives. Still, mammograms also lead to unnecessary treatment for many women while failing to save others, an analysis published this week in JAMA suggests.
The authors take a big-picture look at U.S. data for prostate and breast cancer in the years since screening became widespread. They point out that if a cancer screening test works well and is widely adopted, you should see the rate of early-stage cancer increase and the rate of late-stage cancer decrease, as screening allows doctors to catch potentially deadly cancers at an early, treatable stage. But that’s not what’s happened with prostate and breast cancer rates in this country, they write:
After 2 1/2 decades of screening for breast and prostate cancer, conclusions are troubling: Overall cancer rates are higher, many more patients are being treated, and the absolute incidence of aggressive or later-stage disease has not been significantly decreased. Screening has had some effect, but it comes at significant cost, including overdiagnosis, overtreatment, and complications of therapy …
Arguments of this sort are carrying greater weight among cancer experts these days. The New York Times reports today that the American Cancer Society is working on explaining to patients that screening for breast and prostate cancer carries the risk of overtreating small cancers while missing other, potentially deadly cancers.
“We don’t want people to panic,” the cancer society’s chief medical officer told the NYT. “But I’m admitting that American medicine has overpromised when it comes to screening. The advantages to screening have been exaggerated.”