For women from ages 50 to 69, getting a mammogram saves lives. That's the conclusion of a new review of research. About 7 to 9 lives are saved for every 1,000 women who get mammograms every 2 years, the study found. That benefit outweighs potential harms, the authors concluded. Harms might include anxiety and treatments that some women don't really need. The new analysis was based on studies in Europe and the actual experience of breast cancer screening programs there. It found that about 4 women for every 1,000 tested were "overdiagnosed." This means the cancers found would not have been detected otherwise or caused any problems during their lives. Researchers also estimated other results for each group of 1,000 women tested. About 200 would have at least one recall visit and an extra test that showed they did not have cancer. Of those, 170 would have a test that did not involve surgery. The other 30 would have an invasive procedure (such as a biopsy). Overdiagnosis and extra tests were considered harms because they were not needed. The Journal of Medical Screening published the study. HealthDay News and MedPage Today wrote about it September 13.
By Howard LeWine, M.D.
Harvard Medical School
What Is the Doctor's Reaction?
Women routinely subject their breasts to the often uncomfortable exam called a mammogram. They endure because they believe it can detect breast cancer at an early stage. And catching it early means that it will likely be easier to treat, helping to save lives.
Indeed, a mammogram does find small cancers that no woman or doctor would be able to feel. But more often than not, the worrisome spots detected turn out not to be cancers. These are called false positives. But the spots can't be just ignored. The result is more tests and worry.
Science has been trying for years to weigh the benefits of finding early breast cancers vs. the risks related to false positives. This has led to major debates about the pros and cons of mammograms to screen for breast cancer. Some studies suggest that this test does not live up to the hype. But most experts recommend that women go have regular breast cancer screening with mammograms.
However, well respected groups have had very different opinions about when and how often to do screening. Discussions have focused on:
- Starting routine screening at age 40, rather than 50. There are many more false-positive results in women ages 40 to 49 and fewer breast cancers. The risk of breast cancer increases with age.
- Having a mammogram every other year vs. every year. If there is an advantage to yearly mammograms, it is small. More mammograms also mean more false positives and more radiation exposure.
- Stopping routine mammography at age 75 if an older woman is otherwise healthy.
This new article is based on a review of the results of breast screening on millions of European women. The review supports the advice that women ages 50 to 69 have a mammogram once every 2 years. The researchers estimated that for every 1,000 women screened, 7 to 9 lives were saved.
During the 20-year period when they got mammograms, 200 women out of 1,000 were called back for more tests that did not show any cancer. Of these, 170 received non-invasive testing. The other 30 had invasive tests. Non-invasive tests include a repeat mammogram, an ultrasound and/or an MRI. Invasive procedures include a biopsy and/or surgery.
The results of the review were published online September 13 in The Journal of Medical Screening.
What Changes Can I Make Now?
If you have had some doubts about getting mammograms when you reach age 50, this study should help sway you.
But if you have a higher than average risk of breast cancer, you may need to have regular mammograms starting at a younger age. You also may need to have them more often than once every two years.
Reasons for women to have a higher risk of breast cancer include:
- Family history -- For women who have 2 or more first-degree relatives with breast or ovarian cancer, the chance of developing breast cancer is 50%. A first-degree relative is a mother, daughter or sister.
- Genes -- Some women with a strong family history of breast cancer also have mutations in the BRCA1 or BRCA2 genes. For these women, the lifetime risk of developing breast cancer is 50% to 85%.
- Exposure to radiation -- Women who have had high-dose radiation to the chest have an increased risk of developing breast cancer. Radiation usually was done as part of treatment for another cancer (such as Hodgkin disease). The risk is especially high if a woman had radiation treatment as a teenager.
- Diethylstilbestrol (DES) exposure -- This drug was used from the 1940s through the 1960s to prevent miscarriage. It has since been banned. Women who took DES have a slightly higher risk of developing breast cancer. Their daughters may also.
- Other cancers -- Breast cancer risk is higher in women who have been diagnosed with cancers of the ovary, colon or endometrium.
Other factors also can increase your risk of breast cancer. They might not change how often you need breast cancer screening. But they make it that much more important for you to have routine mammograms. They include:
- Breast density -- A mammogram will show if you have dense breast tissue. Women with dense breasts have a higher risk of breast cancer than women whose breasts contain more fat. The greater the proportion of dense breast tissue on a mammogram, the higher the risk.
- Weight -- Being overweight or obese has been linked to breast cancer risk, especially for women after menopause. However, the relationship is complicated.
- Alcohol -- Women who drink alcohol have a higher risk of breast cancer than women who don't drink. The risk rises with the number of drinks consumed.
What Can I Expect Looking to the Future?
The findings in this review suggest that the U.S. Preventive Services Task Force got it right. The task force recently recommended that women ages 50 to 74 have a mammogram once every 2 years. The group includes experts from several different specialties. So it's highly likely that this is unbiased advice.