Benefits of cancer screening reweighed

The American Cancer Society, which has long been a staunch defender of most cancer screening, is now saying that the benefits of detecting many cancers, especially breast and prostate, have been overstated.

It is quietly working on a message, to put on its website early next year, to emphasize that screening for breast and prostate cancer and certain other cancers can come with a real risk of overtreating many small cancers while missing cancers that are deadly.

"We don't want people to panic," said Dr. Otis Brawley, chief medical officer of the cancer society. "But I'm admitting that American medicine has overpromised when it comes to screening. The advantages to screening have been exaggerated."

Prostate cancer screening has long been problematic. The cancer society, which with more than 2 million volunteers is one of the nation's oldest and largest voluntary health agencies, does not advocate testing for all men. And many researchers point out that the PSA screening test for prostate cancer has not been shown to prevent cancer deaths.

There has been much less public debate about mammograms. Studies from the 1960s to the 1980s found that they reduced the death rate from breast cancer by as much as 20 percent. But it has been unclear how much of the decline is because of mammograms or improved treatment.

The cancer society's decision to reconsider its message about the risks as well as potential benefits of screening was spurred in part by an analysis published Tuesday in the Journal of the American Medical Association, Brawley said.

In it, researchers report a 40 percent increase in breast cancer diagnoses and a near doubling of early stage cancers, but just a 10 percent decline in cancers that have spread beyond the breast to the lymph nodes or elsewhere in the body. With prostate cancer, the situation is similar, the researchers report.

If breast and prostate cancer screening really fulfilled their promise, the researchers note, cancers that once were found late would now be found early, when they could be cured. A large increase in early cancers would be balanced by a commensurate decline in late-stage cancers. That is what happened with screening for colon and cervical cancers. But not with breast and prostate cancer.

Still, researchers say, they do not think all screening will -- or should -- go away. Instead, they hope doctors and the public will understand that the decision to be screened comes with a risk.

For now, that risk is not emphasized in the cancer society's mammogram message, which states that a mammogram is "one of the best things a woman can do to protect her health." Brawley says mammograms can prevent some cancer deaths.

But some, like Colin Begg, a biostatistician at Memorial Sloan-Kettering Cancer Center in New York, worry that the increased discussion of screening's risks is going to confuse the public and make people turn away from screening. He said: "The fact that population screening is no panacea does not mean that it is useless."

The idea that some cancers are not dangerous can be hard to swallow, researchers say. But finding those insignificant cancers is the reason the breast and prostate cancer rates soared when screening was introduced, said Dr. Barnett Kramer, associate director for disease prevention at the National Institutes of Health. And those cancers, he said, are the reason screening has the problem called overdiagnosis -- labeling innocuous tumors cancer and treating them as though they could be lethal when in fact they are not dangerous.

"Overdiagnosis is pure, unadulterated harm," he said.

The new analysis was done by Dr. Laura Esserman, a professor of surgery and radiology at the University of California, San Francisco, and Dr. Ian Thompson, professor and chairman of the department of urology at the University of Texas Health Science Center, San Antonio.

Esserman hopes that as research continues on how to advance beyond screening, distinguishing innocuous tumors from dangerous ones, people will be more realistic about what screening can do. She said, "Just like everything in medicine, there is no free lunch. For every intervention, there are complications and problems."