Doctors tell many American women that they need a yearly mammogram to screen for breast cancer. Early detection saves lives, women are told. But evidence has been mounting for years that mammograms do not reduce the risk of dying from breast cancer.
Last week, the British Medical Journal released a blockbuster long-term study of nearly 90,000 Canadian women. It concluded that yearly mammography screenings for women 40 to 59 do not reduce breast cancer deaths, though they make a diagnosis of breast cancer more likely. That is, the study found that regular mammography leads to more cancers detected but does not lead to fewer women dying of breast cancer.
"We found absolutely no benefit in terms of reduction of deaths from the use of mammography," said study leader Dr. Anthony Miller, an epidemiologist at the University of Toronto's Dalla Lana School of Public Health.
A BMJ editorial bluntly concluded: "Too much mammography."
It won't shock you to know that many people vehemently disagree. The American College of Radiology and the Society of Breast Imaging called the BMJ study "an incredibly misleading analysis" based on a "deeply flawed and widely discredited" previous study. Critics said the Canadian study used outdated equipment and faulty methods that erroneously made mammograms look ineffective.
It's awfully difficult for the public to try to referee this continuing medical debate. What we know: Breast cancer is a fearsome disease. Studies have shown that mammography saves lives. But it also can lead to overdiagnosis, prompting women to undergo unnecessary and potentially harmful treatments. Some tumors are so aggressive that early detection still doesn't save lives. Some cancers progress so slowly that they would never kill.
And remember: The Canadian researchers aren't the first to raise red flags about widespread mammography screenings.
In 2009, the U.S. Preventive Services Task Force set off a firestorm when it recommended most women forgo routine mammograms in their 40s and then test every other year instead of every year. An all-star lineup of doctor's groups and cancer organizations howled that the guidelines would deprive women of a lifesaving test.
One of the panel members on that task force report, Dr. Russell Harris of the University of North Carolina School of Medicine, tells us the latest BMJ study "shows that if mammography makes a difference, it can't be very big. If there were a knock-your-socks-off difference, we would have seen it in this study" because it covers a large number of women over a long time span.
This latest study won't quiet the mammogram controversy. Nor will it dissuade many women from the annual test. In 2010, Americans spent an estimated $7.8 billion for mammography screening, according to a recent study in the Annals of Internal Medicine. The federal government says mammograms are so valuable as a preventive measure that Obamacare requires that they be covered free by insurers.
Many Americans believe that when it comes to screenings, more is always better. More scans, more tests, more detection. That's not necessarily true. Billions of dollars are wasted every year by Americans for unnecessary scans, biopsies and tests. More scans mean more false positive results, which stoke anxiety and prompt even more tests.
Bottom line: What we said in 2009 still holds. Many women know they have a higher than average chance of getting breast cancer, because of family history, a known gene mutation, past exposure to radiation or other risk factors. These women know they have to be vigilant about screening. Others are comfortable with less rigorous monitoring, and the numbers suggest they can afford to relax a little. Some aren't confident where they fall, and many are anxious about that uncertainty. It's not a one-size-fits-all question - it never was - and the conflicting messages within the medical community can be maddening.
Five years later, women have reason to be even more confused and frustrated. All the more reason to follow one simple guideline: The next time your doctor recommends a routine mammogram, ask her why.
Explore further: Annual screening does not cut breast cancer deaths, Canadian study suggests