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.
Since that time, the American Medical Association, the American Congress of Obstetricians and Gynecologists, the American College of Radiology, the National Cancer Institute, and the National Comprehensive Cancer Network all have issued guidelines saying that all women should be eligible for screening mammograms starting at age 40. In 2015, the American Cancer Society recommended that screening mammograms start at age 45.
A study suggests that starting annual screening mammograms at age 40 would save more lives than other mammogram recommendations. Starting annual screening at age 40 also would lead to more false positives, according to the study.
The research was published online on Aug. 21, 2017 by the journal Cancer. Read the abstract of “Comparison of recommendations for screening mammography using CISNET models.”
To do the study, the researchers used statistical models developed by the Cancer Intervention and Surveillance Modeling Network (CISNET) to assess the effects of three sets of screening recommendations on deaths from breast cancer:
- screening mammograms every year from age 40 to age 84 (called annual screening)
- screening mammograms every year from age 45 to age 54, then screening mammograms every other year from age 55 to age 79 (called hybrid screening)
- screening mammograms every other year from age 50 to age 74 (called biennial screening)
For purposes of the study, the researchers assumed that there was 100% compliance with each recommendation.
The researchers then calculated how much each screening recommendation would reduce the number of women who died from breast cancer compared to no screening at all:
- annual screening reduced mortality by 39.6%
- hybrid screening reduced mortality by 30.8%
- biennial screening reduced mortality by 23.2%
In a single year, for women who were 40 years old, the number of deaths from breast cancer prevented would be:
- 29,369 for annual screening
- 22,829 for hybrid screening
- 15,599 for biennial screening (based on 2016 CISNET estimates)
The researchers then calculated the total number of mammograms that would be done, the number of recalls for false positives, and the number of biopsies done because of false positives for each recommendation.
Annual screening would result in:
- 90.2 million mammograms per year
- 6.8 million recalls for false positives
- 481,269 biopsies because of false positives
Hybrid screening would result in:
- 49 million mammograms per year
- 4.1 million recalls for false positives
- 286,288 biopsies because of false positives
Biennial screening would result in:
- 27.3 million mammograms
- 2.3 million recalls for false positives
- 162,885 biopsies because of false positives
"Our findings are important and novel because this is the first time the three most widely discussed recommendations for screening mammography have been compared head to head," first author Elizabeth Kagan Arleo, M.D., of Weill Cornell Medicine, said in a statement. "Our research would be put to good use if, because of our findings, women chose to start annual screening mammography at age 40. Over the long term, this would be significant because fewer women would die from breast cancer."
The researchers pointed out that the different screening recommendations did have trade-offs.
"If the screening program goal is to perform as few mammograms as possible to achieve limited benefit and fewer risks …then the optimal age of initiation may be 50 years with an optimal frequency of biennial screening ending at age 74," the researchers concluded. "On the other hand, if the goal is to avert the most breast cancer deaths and gain the most life-years, [this] modeling shows that the optimal age of initiation for screening mammography is 40 years, the optimal screening frequency is annual, and the optimal stopping age is when a woman's life expectancy is less than 5 to 7 years."
At Breastcancer.org, we believe that a woman’s best chance for early detection requires coordination of our current screening tools:
- high-quality mammography
- clinical breast exam
- breast self-exam
To not use all three tools are missed opportunities for early detection.
The reality is that every woman is at risk for breast cancer, and this risk tends to increase over time. It’s important to understand and regularly update your health information related to breast cancer risk throughout your life with your doctor. To get the conversation started, here are some points to talk to your doctor about:
- family history of breast or other related cancers (ovarian, melanoma)
- any test results for abnormal genes linked to a high risk of breast cancer
- results of past breast biopsies, even if they were benign
- personal history of being treated with radiation to the face and/or chest before age 30
- breast density
- weight, if you’re overweight or obese
- level of physical activity
- any use of postmenopausal combined hormone replacement therapy (HRT)
- alcohol consumption, if you regularly drink more than 3 alcoholic beverages per week
- the amount of processed food and trans fats you eat
- your smoking history
- whether or not you had a full-term pregnancy or breastfed
Breastcancer.org stands by its recommendation that all women have mammograms annually starting at age 40, and the results of this study strongly support that recommendation. We also believe that monthly breast self-exam and annual physical exams by a doctor are essential parts of an overall breast cancer screening strategy. If you’re at high risk for breast cancer, you should talk to your doctor about starting annual mammograms at a younger age and consider other screening tools (such as MRI or ultrasound) to maximize the opportunity for early detection.
For more information on mammograms, including where to get one and the benefits and risks, visit the Breastcancer.org Mammograms page.