Starting Mammograms at Age 40 Saves Lives

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In the United States, recommendations call for annual screening mammograms to start at age 40. Research analyses, including one by the U.S. Preventive Services Task Force, have questioned the value of routine breast cancer screening in women younger than 50. So some doctors and screening experts recommend that routine screening begin at age 50 instead of 40.

A very large Swedish study found that every-other-year screening starting at age 40 saves lives. Women who started getting screening mammograms at age 40 instead of 50 were 26% less likely to die from breast cancer. These results were presented at the 2010 American Society of Clinical Oncology (ASCO) Breast Cancer Symposium.

Sweden has a national health system so healthcare tends to be the same throughout the country. A national heath system also makes it easier to track health outcomes.

In 1986, Sweden's health system established mammogram guidelines for breast cancer screening. Women aged 40 to 49 had the option to get every-other-year mammograms. About half of the counties in Sweden invited women aged 40 to 49 to get screening mammograms. All Swedish counties supported screening mammograms for women 50 and older.

So about half of Swedish women started getting screening mammograms at age 40 to 49 and the other half started at age 50. This situation allowed researchers to study the benefits of screening mammograms for women aged 40 to 49 because they could compare the health records of women screened at age 40 to 49 to the records of woman screened starting at age 50. The researchers looked at the health records of more than 600,000 Swedish women in this exceptionally large study.

Overall, women who started getting screening mammograms at age 40 instead of 50 were 26% less likely to die from breast cancer. Still, not all the women in the counties that supported screening mammography for women aged 40 to 49 actually had mammograms every other year. In a separate analysis, the researchers looked only at the records of women who consistently had mammograms every other year from age 40 to 49. These women were 29% less likely to die of breast cancer compared to women who didn't start getting mammograms until age 50.

One way to rate the value of a screening test is to figure out how many tests have to be done to save one life. The cost of the test is also considered. Besides the cost of doing and reading each mammogram, researchers also consider the cost associated with false positives. A false positive is an abnormal area that looks like a cancer on a mammogram but turns out to be normal. Mammograms are not perfect tests and false positives happen. Besides the fear of a breast cancer diagnosis, a false positive usually means more tests (including biopsies) and follow-up doctor visits. The process can be very stressful and upsetting.

This study showed that screening 1,250 women every other year from ages 40 to 49 (6,250 mammograms total) would save one life. This study and other research has shown that screening a smaller number of women age 50 and older saves one life. This means that while screening women age 40 to 49 has clear benefits, the benefits are not as great as screening women age 50 and older.

Regular screening mammograms starting at age 40 help diagnose breast cancer early, when it's most treatable. This study shows that mammograms starting at age 40 save lives. If you are 40 or older and have an average risk of breast cancer, regular screening mammograms should be a part of your healthcare. If your breast cancer risk is higher than average, you may want to talk to your doctor about a more aggressive breast cancer screening plan that makes the most sense for your particular situation.

For more information on mammograms and other tests to detect breast cancer, visit the Screening and Testing section.

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