A large study has cast doubt on the benefits of regular mammograms to screen for breast cancer, adding to the already heated debate about what has become an annual ritual for many middle-aged American women.
Radiologists have come out with an unusually strong pushback, calling the new study flawed, and the American Cancer Society says it's still best to screen—leaving women more confused than ever about what to do.
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The study was done by a team in Toronto, Canada. They watched nearly 90,000 women aged 40 to 59 for 25 years who were randomly assigned to either have mammograms every year for five years, or an occasional physical breast exam.
They found that the screening didn't save lives, and 22 percent of the women screened got diagnosed with cancers that would never have harmed them. They said 180 women who got mammograms died of breast cancer over the 25 years, compared to 171 who didn't get mammograms.
"The rationale for screening by mammography should be urgently reassessed by policy makers," Anthony Miller of the University of Toronto and colleagues wrote in their report, published in the British Medical Journal.
Mounting evidence against mammograms
Other studies have done little to change the minds of women in the U.S., federal policymakers or even the American Cancer Society.
But the new research supports the European approach, and advice from an expert U.S. committee that's said women can cut back on the mammograms if they want.
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The U.S. Preventive Services Task Force, appointed to guide the federal government on medical policy, said in 2009 that women should not start routine mammograms until age 50 because studies have shown the tests have such high false positive rates and any benefits in lives saved did not outweigh the worry and potential overtreatment of women diagnosed with cancers that wouldn't have caused symptoms.
Last March, a study showed that many women suffer intense anguish after they get called for a follow-up mammogram when a radiologist has spotted something suspicious.
In 2012, another study, published in the New England Journal of Medicine, found that as many as a third of cancers detected through routine mammograms may not be life-threatening. They said 1 million women may have been overdiagnosed, which means they were needlessly treated, not to mention emotionally distressed.
And a study published last February found that women aged 50 to 74 who got screened every other year were no more likely to have advanced stage cancer or big tumors than women screened more frequently — even if they had so-called dense breasts, which are harder to read on an X-ray.
Screening still recommended
But the American Cancer Society stands firmly on the side of mammograms. "If you are a woman 40 or over, you should get a mammogram every year," it advises.
"Current evidence supporting mammograms is even stronger than in the past," it adds. "In particular, recent evidence has confirmed that mammograms offer substantial benefit for women in their 40s. Women can feel confident about the benefits associated with regular mammograms for finding cancer early. However, mammograms also have limitations. A mammogram can miss some cancers, and it may lead to follow up of findings that are not cancer."
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Doctors worry about sending mixed messages to women. Screening the right women can save lives, and there are fears that women may just give up and skip screening altogether if they fear it won't do them any good. And women with a high risk of breast cancer—for example, those with a family history of the disease—do need to start screening early.
The American College of Radiology called the study "deeply flawed" and said new and better treatments for breast cancer do save lives. Many breast cancer experts also say the recovery from treating a very small breast tumor is much less than if a woman's cancer has grown and spread.
The best advice? Getting a mammogram is a personal decision, and women need to weigh their desire to feel on top of the risks versus how they would feel if they did get called back to check out something suspicious. It's the old cliché—talk with your doctor about what is best for you.
Breast cancer is a leading killer of U.S. women. Every year it's diagnosed in 200,000 women and a few men, and kills around 40,000.
—By NBC News' Maggie Fox