Breast Cancer Screening for Women at Average Risk

Breast cancer is a leading cause of mortality among US women.  About 200,000 women are being diagnosed every year in the US with breast cancer and 40,000 women die from the disease.

Despite the interest and research on breast cancer screening, there is uncertainty about mammography’s benefits versus potential harms from false positives and overdiagnosis.  Thus recommendations on the frequency of its use are wide-ranging.  Different countries and professional societies have guidelines recommending from annual to biennial to triennial or no screening at all.   

In 2003, the American Cancer Society (ACS) recommended annual mammography screening for all women starting at age 40 years and continuing as long as a woman remained in good health.  The ACS also recommended clinical breast examination (CBE) periodically for women in their 20s and 30s and annually for women 40 years and older.

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The ACS has revised its guidelines regarding when and how often women at average risk should receive screenings for breast cancer.

The ACS commissioned a systematic evidence review in 2015 of the breast cancer screening literature and a supplemental analysis of mammography registry data to address questions related to the screening interval.

 Formulation of recommendations was based on the quality of the evidence and judgment about the balance of benefits and harms such as biopsies resulting from false positive mammograms.

Screening mammography in women aged 40 to 69 years is associated with a reduction in breast cancer deaths to as much as 30 percent, and inferential evidence supports breast cancer screening for women 70 years and older that are in good health.  Evidence does not support routine clinical breast examination as a screening method for women at average risk.

Oeffinger et al review and analysis are described in their paper in JAMA and form the basis of the new ACS recommendations that are:

·      - Women with an average risk of breast cancer should undergo regular screening mammography starting at age 45 years (strong recommendation).

·      - Women aged 45 to 54 years should be screened annually (qualified recommendation).

·     -  Women 55 years and older should transition to biennial screening (strong recommendation).

·     -  Women should have the opportunity to begin annual screening between the ages of 40 and 44 years (qualified recommendation).

·     -  Women should continue screening mammography as long as their overall health is good and they have a life expectancy of 10 years or longer (qualified recommendation).

The ACS does not recommend clinical breast examination for breast cancer screening among average-risk women at any age (qualified recommendation).

These updated ACS recommendations bring it closer to the draft guidelines released on April 20, 2015, by the U.S. Preventive Services Task Force (USPSTF) for breast cancer screening which are:

·      For women at average risk for breast cancer, most of the benefit of mammography will result from biennial screening during ages 50 to 74 years.

·      Of all age groups, women ages 60 to 69 years are most likely to avoid a breast cancer death through mammography screening.

·      Screening mammography in women ages 40 to 49 years may reduce the risk of dying of breast cancer, but the number of deaths averted is much smaller than in older women and the number of false-positive tests and unnecessary biopsies are larger.

·      Women with a parent, sibling, or child with breast cancer may benefit more than average-risk women from beginning screening between the ages of 40 and 49 years.

·      The USPSTF concludes that the current evidence is insufficient to assess the balance of benefits and harms of screening mammography in women age 75 years and older.

·      The USPSTF concludes that the current evidence is insufficient to assess the benefits and harms of tomosynthesis (3-D mammography) as a screening modality for breast cancer.

The ACS and USPSTF guidelines are now more consistent and state that the decision to start screening mammography prior to age 50 years should be an individual one. Both guidelines agree that for average-risk women younger than 45 years, the harms from false positive screening mammograms outweigh the benefits. For women older than 55 years, biennial mammography is likely to provide the most benefits while limiting the harms. The new ACS recommendation to stop screening for older women with life expectancies of less than 10 years is consistent with the emphasis on functional versus chronologic age.  ACS is also recommending ending physical for screening purposes by doctors entirely.

These recommendations do not apply to women age 40 years and older who are at high risk because pre-existing breast cancer or a previously diagnosed high-risk breast lesion and who are known to have underlying genetic mutation (such as a BRCA mutation or other familial breast cancer syndrome) or a history of chest radiation at a young age.  Women at high risk for developing breast cancer will require a more personalized screening than the vast majority of women who are at average risk.

There will be many professional societies and well meaning doctors who will disagree with the new guidelines from ACS and USPSTF but until and when a well designed prospective randomized study provides findings that differ with the above mentioned recommendations they will likely stand.