Women with Family History of Breast Cancer Benefit from Mammograms Starting at 40

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United States guidelines recommend that annual screening mammograms start at age 40. Still, some studies, 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 start at age 50 instead of 40.

A study suggests that screening mammograms in women aged 40 to 50 with a family history of breast cancer are beneficial.

Health care in the United Kingdom is through the National Health System (NHS). This system makes it a little easier to track health outcomes and do research on the benefits of screening, including mammograms.

In this study, 6,170 healthy British women aged 40 to 50 agreed to have yearly screening mammograms and be followed for at least 4 years. Most of the women enrolled in the study when they were younger than 45, so would have at least five screening mammograms before they were 50.

All of the women had a family history of breast and/or ovarian cancer in at least one first- or second-degree relative. Because of this family history, all the women were considered to have a higher-than-average risk of breast cancer. Still, none of the women were considered to be at high risk for breast cancer.

The women weren't tested for an abnormal breast cancer gene (BRCA1 or BRCA2). The researchers didn't allow women who were considered to be at very high risk based on personal and family health history to participate in the study; so they thought that few, if any, participating women had an abnormal breast cancer gene.

To determine the benefits of breast cancer screening for women younger than 50, the researchers compared the outcomes of the women in this study to the outcomes of women in two other studies. One was the U.K. Age Trial that involved more than 100,000 women who weren't screened until age 50. The other study involved 238 Dutch women with a family history of breast cancer who had been diagnosed with invasive breast cancer.

In this study, 105 breast cancers were detected by screening mammograms done before age 50. Another 31 breast cancers were detected by breast self-exam or a doctor's physical exam.

Compared to breast cancers diagnosed in women in the U.K. Age Trial and the Dutch study, the breast cancers diagnosed in the women who had screening mammograms in their 40s were:

  • more likely to be small
  • less likely to have lymph node involvement
  • more likely to be grade 1 and less likely to be grade 2 or 3; higher grade cancers tend to be more aggressive and more difficult to treat

The researchers concluded that annual screening mammograms before age 50 had prevented five breast cancer-related deaths among the 6,170 women in the study. Overall, the estimated risk of dying from breast cancer was 20% lower when mammograms started before age 50 compared to the risk when mammograms started at age 50.

One way to determine the value of a screening test is to figure out how many tests have to be done to save one life. Based on this study's results, the researchers concluded that 5,000 screening mammograms saved one life.

Researchers also consider the problems associated with false positives when evaluating the benefits of screening. 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 found that while women who had false positives were highly anxious, the anxiety lasted only a short time and was much lower 6 months after the false positive result.

Regular screening mammograms starting at age 40 help diagnose breast cancer early, when it's most treatable. This study shows that screening mammograms starting before age 50 save lives in women with slightly higher-than-average risk. This study, along with many others, supports the Breastcancer.org recommendation that if you are 40 or older and have an average risk of breast cancer, regular screening mammograms should be a part of your healthcare. Screening in your 40s is especially important if you have a family history of breast cancer. If your breast cancer risk is considered much 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 Breastcancer.org Screening and Testing section.

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