For years, women have heard a warning that made plenty of them skip their next mammogram: Screening finds lots of cancers that never would cause any harm, and many women end up getting treated for nothing.
Some estimates put that overdiagnosis as high as 30% to 50% of the cancers screening finds. That’s a scary number. It’s also, according to a recent analysis, wrong.
Researchers led by Sisse Helle Njor, a professor at the University of Southern Denmark, went back to all eight of the big randomized mammography trials and ran the numbers again. Their conclusion, published in the Journal of the National Cancer Institute: Overdiagnosis is likely under 5%.
That matters, because bad information keeps women away from a test that works. The American Cancer Society expects about 321,910 new cases of invasive breast cancer and about 42,140 deaths from breast cancer this year.
And the breast cancer death rate has fallen 44% since 1989, thanks largely to earlier detection and better treatment.
Here are five myths that keep women from getting screened — and what the evidence actually says.
1. ‘Mammograms find lots of cancers that don’t need treatment’
This is the myth the study takes aim at.
Overdiagnosis is real: Screening can find a slow-growing cancer that never would have caused a problem in a woman’s lifetime. The question has always been how often it happens.
The earlier, higher estimates relied on trial data before it had fully matured, according to the research team’s summary of the findings.
The analysis adjusted for how long the trials followed women, how many screening rounds were offered and the fact that women in the comparison groups often got screened after the trials ended.
The result: “randomized trial data are consistent with overdiagnosis of less than 5%,” said co-author Matejka Rebolj, a senior epidemiologist at Queen Mary University of London.
Expect some pushback. Researchers have argued about this number for decades, and one study won’t end the debate. But the original trials themselves no longer support the 30%-to-50% figure.
2. ‘Nobody in my family had it, so I’m low-risk’
A family history does raise your risk. Having a mother, sister or daughter with breast cancer almost doubles it, according to the American Cancer Society.
But here’s the part that surprises people: Most women who get breast cancer have no family history of the disease, according to the National Institutes of Health.
In other words, a clean family tree isn’t a reason to skip the test. About 1 in 8 women will develop breast cancer at some point.
3. ‘I don’t feel a lump, so I don’t need one’
That’s exactly backward. The whole point of a mammogram is to find cancer before you can feel it.
Regular mammograms can catch breast cancer early, sometimes up to three years before it can be felt, according to the Centers for Disease Control and Prevention. Cancers caught early are far easier to treat.
Nearly two-thirds of breast cancers are found while still confined to the breast, and five-year survival at that stage is essentially 100%, according to the National Cancer Institute.
One more thing: A normal result isn’t always the whole story. About half of women over 40 have dense breast tissue, which can make cancers harder to spot on a mammogram, according to the Food and Drug Administration.
Your mammogram report now has to tell you whether you do. If it says your breasts are dense, ask your doctor whether you need anything more.
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4. ‘I’m past 65, so what’s the point?’
Breast cancer is mostly a disease of older women. The median age at diagnosis is 64, and nearly half of new cases are diagnosed in women 65 and older, according to the National Cancer Institute’s SEER program.
The U.S. Preventive Services Task Force, the independent panel whose advice doctors and insurers follow, recommends a mammogram every two years for women 40 to 74. That means your 60s and early 70s are squarely in the screening years.
After 75, it gets more personal. The task force says there isn’t enough evidence to make a blanket call, so it’s a decision to make with your doctor based on your health.
We’ve written about tests that may not make sense later in life. But “I’m 67” isn’t a reason to stop.
5. ‘It’s not worth the cost — or the radiation’
If you’re on Medicare, cost shouldn’t stop you. Medicare covers a screening mammogram once every 12 months for women 40 and older, and you pay nothing if your provider accepts assignment.
Know the difference, though. If your doctor orders a diagnostic mammogram to check a problem, you’ll generally owe 20% of the Medicare-approved amount after your Part B deductible.
Not on Medicare and short on cash? Here’s where to get a low-cost or free mammogram.
As for radiation, the dose is small. A standard screening mammogram delivers about what you’d absorb from natural background radiation over roughly a month, according to RadiologyInfo.org, which is run by the American College of Radiology and the Radiological Society of North America.
The bottom line
For decades, a shaky statistic gave women an excuse to put off one of the few cancer screenings proven to save lives. The trials behind that statistic now tell a different story.
If you’re due, book it. If you’re 75 or older, talk it through with your doctor. And if someone tells you mammograms mostly find cancers that don’t matter, you now know the better answer.
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