Several large studies have questioned the value of screening mammograms, 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.
But a study using data from Sweden has found that women diagnosed with breast cancer who had regular mammograms had a 60% lower risk of dying from the disease in the 10 years after diagnosis and a 47% lower risk of dying from the disease in the 20 years after diagnosis compared to women who didn’t have regular screening.
The research was published online on Nov. 8, 2018, by the journal Cancer. Read "The incidence of fatal breast cancer measures the increased effectiveness of therapy in women participating in mammograph screening."
The mammogram controversy
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.
Does screening improve breast cancer survival?
Researchers did the study reviewed here because they wanted to answer an important question: If a woman chooses to participate in regular mammography screening, then how much will this choice improve her chances of survival if she is diagnosed, compared to women who choose not to have regular screening mammograms?
To answer the question, the researchers looked at the records of about 52,440 women aged 40 to 69 in the county of Dalarna, Sweden, from 1958 to 2015. Starting in 1977, about 66% of women aged 40 to 69 were regularly invited to have a mammogram as part of a study. From 1986 on, all women aged 40 to 69 were regularly invited to have a mammogram.
During the study period, 4,513 women were diagnosed with breast cancer. Of these women who were diagnosed, 3,231 could be followed for 20 years after diagnosis, including:
- 1,225 who were diagnosed before 1977, when regular screening started
- 2,006 who were diagnosed after 1977
Another 1,281 women who were diagnosed with breast cancer from 1996 to 2005 could be followed for 10 years after diagnosis.
Overall, 1,061 women died from breast cancer within 10 years of diagnosis:
- 552 were diagnosed before regular screening started.
- 509 were diagnosed after regular screening started.
And 213 women died from breast cancer 11 to 20 years after diagnosis:
- 87 were diagnosed before regular screening started.
- 126 were diagnosed after regular screening started.
If diagnosed with breast cancer, women aged 40 to 69 who had regular screening mammograms were 60% less likely to die from the disease in the first 10 years after diagnosis than women who didn’t have regular screening mammograms.
Eleven to 20 years after diagnosis, women aged 40 to 69 who had regular screening mammograms were 47% less likely to die from the disease compared to women who didn’t have regular screening mammograms.
“Although some consider that advances in adjuvant therapy and chemotherapy mainly are responsible for improved breast cancer prognosis in screened populations in the modern era, we believe that it is time to focus attention on the combination of diagnosis and therapy, instead of viewing them as independent, or worse, as competing interests,” the researchers wrote. “Our results demonstrate that the benefit of therapy is significantly greater for women who have participated in mammography screening.”
Your best chance for early detection
At Breastcancer.org, we believe that a woman’s best chance for early detection of breast cancer requires coordination of our current screening tools:
- high-quality mammography
- clinical breast exam
- breast self-exam
To not use all three tools is a missed opportunity 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.
Written by: Jamie DePolo, senior editor
Reviewed by: Brian Wojciechowski, M.D., medical adviser