A Norwegian study suggests that screening mammograms don't save as many lives as was previously thought. Still, the results are controversial and some researchers, as well as Breastcancer.org experts, are concerned about the design of the study.
Norway began a national breast cancer screening program in 1996. The program started in just four counties and gradually expanded over the next 9 years. The entire country now participates in the program, which allows women age 50 to 69 to get a mammogram every 2 years.
To see if screening mammograms reduced the number of Norwegian women dying from breast cancer, the researchers compared the health records of women diagnosed with breast cancer who lived in a county with screening to the health records of women diagnosed with breast cancer who lived in a county with no screening.
The researchers found that the number of women dying from breast cancer dropped by 28% in counties with screening compared to counties with no screening. But they calculated that only about a third of this decline was because of screening mammograms. The researchers said most of the decline was because of other factors that improved breast cancer survival, including the creation of breast cancer management teams to treat people diagnosed with breast cancer. The breast cancer management teams were available throughout Norway to anyone whether or not they were eligible for the screening program.
The research showed that mammograms DO save lives, especially for women diagnosed with stage II breast cancer. Still, because the reduction in breast cancer deaths was small -- a 10% percent reduction works out to be 0.4 fewer deaths per 1,000 women over 10 years -- some experts are concerned that the United States may consider changing its screening mammogram guidelines. They're especially concerned because the U.S. Preventive Services Task Force recommended delaying screening mammograms until age 50 in November 2009. Breastcancer.org strongly disagreed with the task force's recommendations, as did other breast cancer experts. Because of these concerns, the recommendations have not been implemented.
Breastcancer.org also is concerned about the design and other aspects of the Norwegian study reviewed here:
- Women in this study got screening mammograms every 2 years instead of every year, as U.S. recommendations advise. So some of the benefits of screening mammograms could be lost because of this time lag.
- The study only looked at breast cancer in Norwegian women -- a much different population than U.S. women. Norwegian women are more alike than women are in the United States, which is a much bigger melting pot of ethnicities. Norwegian women also have access to a national health care program from the time they're born. Many women in the United States don't have insurance and can't afford health care.
- Breast cancer has to be detected before it can be treated. Mammograms are probably the most important tool doctors have to find breast cancer. This study suggests that most of the increase in survival was because of better treatment -- but if screening mammograms didn't find the cancers, what did?
- The number of women dying from breast cancer is one way to measure the success of screening mammograms. Still, there are other results that are important to women diagnosed with the disease. Having a shorter or less severe course of treatment -- surgery and radiation compared to surgery, radiation, and chemotherapy, for example -- is a result that many women would like. Screening mammograms can find breast cancers early, when they're likely to be smaller and more treatable.
- This study didn't include women age 40 to 49. Breast cancer in younger women tends to be more aggressive, so early diagnosis and treatment is important for them. It's possible that screening mammograms may contribute greatly to the survival of younger women diagnosed with breast cancer.
Breastcancer.org believes that all medical decisions, including if and when to screen for breast cancer, are individual decisions to be made by each woman in consultation with her doctor. Talk to your doctor about your family and personal health history and your individual risk of breast cancer. Together you can create a screening plan that makes the most sense for you and your unique situation.