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Mammography Screening Guidelines

How old should a woman be when she has her first mammogram? How often should she have a mammogram?

Not all experts agree on the answer to this question. If a woman is at average risk:

United States Preventive Services Task Force:

  • Ages 40-49:  The USPSTF says the decision to start screening mammography in women before age 50 years should be an individual one. Women who place a higher value on the potential benefit than the potential harms may choose to begin screening every two years between the ages of 40 and 49 years.
  • Ages 50-74: The USPSTF recommends screening mammography every two years for women ages 50 to 74 years.
  • Women 75 and older: The current evidence is insufficient to assess the balance of benefits and harms of screening mammography in women 75 years and older.

American Cancer Society:

  • Women ages 40 to 44 should have the choice to start annual breast cancer screening with mammograms if they wish to do so. The risks of screening as well as the potential benefits should be considered.

  • Women age 45 to 54 should get mammograms every year.

  • Women age 55 and older should switch to mammograms every 2 years, or have the choice to continue yearly screening.

As these guidelines show, there is general agreement that women 50 years of age and older should have mammograms. But there is a longstanding controversy as to whether women between the ages of 40 and 49 should also have routine mammography screening.

Some people say: What’s the harm? Why not screen? There are a couple of reasons:

  • Women between 40 and 49 typically have denser breast tissue. On a mammogram, this dense breast tissue shows up as white—which is the same color as a cancer appears on a mammogram. With menopause, which typically begins around age 50, the dense tissue in women's breasts is replaced with fatty tissue, which looks gray on a mammogram. It is much easier to see the white cancer against this gray background. That's why mammography works better on women aged 50 and older.
  • Many abnormalities seen on mammograms may not be cancer (these are called false positives), but they will prompt additional testing and anxiety. In fact, as many as three out of 10 women who begin annual screening at age 40 will have an abnormal mammogram during the next decade, and the majority of these will end up having biopsies—only to learn that the test was a false positive.
  • To date, eight randomized controlled trials have found that mammography screening for women between 40 and 49 had no effect on mortality.

Why would this be? Mammography is far from a perfect screening tool. It may help you find your cancer early, but finding a cancer "early" is not a guarantee that your life will be saved. We now know there are different types of cancers and how quickly a cancer progresses has more to do with the type of cancer a woman has than when it is found.

Not sure what to do? Probably the best way for a woman to decide when to begin having mammograms is for her to discuss personal risk factors for breast cancer with her physician.

Decision Aids

These tools can help women better understand the benefits and risks of mammography and make better informed decisions about when to start screening:

  • Breast Screening Decisions

A Mammogram Decision Aid for Women Ages 40-49  Public Health Agency of Canada: Mammography for Women 40 and Over

A Decision Aid for Breast Cancer Screening Australian Screening Mammography Decision Aid

A Decision Aid for Women Aged 40 Thinking About Starting Mammography Screening