Several large studies, including a review by the U.S. Preventive Services Task Force in 2009 and a study on the causes of death in the United Kingdom in 2013, have questioned the value of screening mammograms.
Doctors who question the value of mammograms say that while mammograms do save lives, for each breast cancer death prevented, three to four women are overdiagnosed. Overdiagnosis means either:
- a screening mammogram finds a suspicious area that would have been eventually diagnosed as cancer by other means, without any effect on prognosis
- a screening mammogram finds a suspicious area that never would have affected a woman’s health if it hadn’t been found or treated
False positive results from screening mammograms also have helped fuel the debate about the value of breast cancer screening. When a mammogram shows an abnormal area that looks like a cancer but turns out to be normal, it’s called a false positive. Ultimately the news is good: no breast cancer. But the suspicious area usually requires follow-up with more than one doctor, extra tests, and extra procedures, including a possible biopsy. There are psychological, physical, and economic costs that come with a false positive.
These studies and the resulting stories in the media have fueled an ongoing debate about the value of screening mammograms.
To help settle the discussion, a group of researchers at Harvard Medical School’s Department of Health Care and Policy and Brigham and Women’s Hospital reviewed 50 years’ worth of international studies looking at the benefits and risks of screening mammography.
The results suggest that the benefits of screening are often overestimated, while the risks are underestimated. The researchers also found that since the benefits and risks of screening mammograms are affected by complex medical factors and personal preferences, doctors and women need to develop a very individualized approach to breast cancer screening.
The research was published on April 1, 2014 by JAMA. Read “A Systematic Assessment of Benefits and Risks to Guide Breast Cancer Screening Decisions.”
In the same issue of JAMA, other Harvard experts along with experts from the University of California-San Francisco reviewed studies done from 1990 to 2014 looking at the benefits of mammograms for women ages 75 and older. These experts concluded that mammograms offered limited benefits to older women and should only be recommended for women who are expected to live for at least 10 more years.
Read the abstract of “Screening Mammography in Older Women: A Review.”
An individualized approach to mammography
In the analysis of international studies on the benefits and risks of screening mammograms done in the last 50 years, the researchers found that about 19% fewer women died because of an annual mammogram:
- for women in their 40s, this percentage was lower: about 15%
- for women in their 60s, this percentage was higher: about 32%
Still, how much any individual woman benefits from a screening mammogram depends on her personal risk of breast cancer.
So it makes sense that women older than 50 would get more benefits from screening mammograms because the risk of breast cancer is higher for an average woman in her 50s or 60s than it is for an average woman in her 40s.
The researchers estimated that if 10,000 women in their 40s had an annual mammogram for 10 years, about 190 of the women would be diagnosed with breast cancer. Of these 190 women:
- about 5 will not die from breast cancer because of a screening mammogram
- about 25 will die from breast cancer whether or not they had a mammogram
- the rest of the women will survive, mainly because of better breast cancer treatments
The researchers said that overdiagnosis is the biggest risk of screening mammograms. They estimated that about 19% of women diagnosed with breast cancer are overdiagnosed. This means that about 36 of the 190 women diagnosed with breast cancer would have been treated with what the researchers called unnecessary surgery, chemotherapy, or radiation.
Besides age, other factors, such as family history, genetics, drinking alcohol, smoking, and not exercising also affect breast cancer risk. This is why the researchers believe that it’s important for each woman to have a screening plan based on her individual breast cancer risk, not a national average.
“I have 80-year-olds in my practice with life expectancies of 15 or 20 years, and 60-year-olds who will likely only live another year or two,” said Nancy Keating, co-author of the study, professor of health care policy at Harvard Medical School, and professor of medicine at Brigham and Women’s Hospital. “Those two kinds of patients need different recommendations about whether to continue screenings, and it can’t be based simply on the patient’s age.”
The researchers said they hope that the study will encourage doctors to develop tools to customize screening plans based on each woman’s needs.
But until those tools are created, it’s important to make sure you get an annual mammogram.
If you're 40 or older and have an average risk of breast cancer, yearly screening mammograms should be part of your healthcare. If your breast cancer risk is higher than average, you should talk to your doctor about a more aggressive breast cancer screening plan that makes the most sense for your particular situation.
There's only one of you and you deserve the best care possible. Don't let any obstacles get in the way of your regular screening mammograms:
- If you're worried about cost, talk to your doctor, a local hospital social worker, or staff members at a mammogram center. Ask about free programs in your area.
- If you're having problems scheduling a mammogram, call the National Cancer Institute (800-4-CANCER) or the American College of Radiology (800-227-5463) to find certified mammogram providers near you.
- If you find mammograms painful, ask the mammography center staff members how the experience can be as easy and as comfortable as possible for you.
Should women older than 75 get mammograms?
Building on the idea that breast cancer screening plans need to be customized, a second group of Harvard experts, along with experts from the University of California-San Francisco, concluded that doctors should focus on life expectancy when recommending mammograms for women ages 75 and older.
The researchers reviewed mammogram studies done between 1990 and 2014 and found that none of the studies included women age 75 or older. So there’s no scientific evidence that mammograms help save the lives of these older women.
Some of the studies used computer software to create models of the risks and benefits of mammograms for women ages 75 and older. The researchers estimated that screening mammograms would prevent two women from dying of breast cancer for every 1,000 women in their 70s who were screened every 2 years for 10 years. Still, the researchers also estimated that about 200 of every 1,000 women would get false positive results or be overdiagnosed and receive unnecessary treatment.
It’s important to know that a typical 75-year-old woman will live another 11 years on average. And many women aren’t average in terms of health status, life expectancy, or risk of dying from breast cancer or another disease. Nearly all experts would agree that annual screening doesn’t make sense for an older woman who wouldn’t want to be treated for breast cancer because of personal preferences or other health issues. Still, many women ages 75 and older are in reasonably good health and would want to be treated should they be diagnosed.
Breastcancer.org believes that the importance of diagnosing breast cancer early, when it’s most treatable, doesn’t get any less important as a woman gets older. Regular screening mammograms make sense for any woman age 75 and older who would want to be treated for breast cancer should she be diagnosed.
For more information on mammograms and other tests to detect breast cancer, visit the Breastcancer.org Breast Cancer Tests: Screening, Diagnosis, and Monitoring pages.
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