Recommendation Statement From USPSTF: Screening for Breast Cancer

US Preventive Services Task Force (USPSTF)

Disclosures

December 17, 2009

In This Article

Other Considerations

Implementation

The Task Force on Community Preventive Services has reviewed the evidence on methods to increase breast cancer screening, including reminder systems and other interventions.[3,4,5]

Explanation of Change in Recommendation

The 2002 USPSTF issued a B recommendation for screening mammography for women 40 years or older. However, it went on to say:

The precise age at which the benefits from screening mammography justify the potential harms is a subjective judgment and should take into account patient preferences. Clinicians should inform women about the potential benefits (reduced chance of dying from breast cancer), potential harms (for example, false-positive results, unnecessary biopsies), and limitations of the test that apply to women their age. Clinicians should tell women that the balance of benefits and potential harms of mammography improves with increasing age for women between the ages of 40 and 70.[6]

The updated USPSTF recommendation endorses this approach to deciding when to start screening. However, the current USPSTF is now further informed by a new systematic review,[7] which incorporates a new randomized controlled trial that estimates the "number needed to invite for screening to extend one woman's life" as 1904 for women aged 40-49 years and 1339 for women aged 50-59 years. Although the relative risk (RR) reduction is nearly identical (15% and 14%, respectively) for these 2 age groups, the risk for breast cancer increases steeply with age starting at 40 years old. Thus, the absolute risk reduction from screening (as shown by the number needed to invite to screen) is greater for women aged 50-59 years than for those aged 40-49 years.

The current USPSTF statement is also informed by the Cancer Intervention and Surveillance Modeling Network (CISNET) modeling studies[8] that accompany this recommendation. The Task Force considered both "mortality" and "life-years gained" outcomes. In this case, given that the age groups (40-49 years and 50-59 years) are adjacent, the Task Force elected to emphasize the mortality outcomes from the modeling studies. Of the 8 screening strategies found most efficient, 6 start at age 50 years rather than age 40 years. The frontier curves for the mortality outcome show only small gains but larger numbers of mammograms required when screening is started at age 40 years vs age 50 years.

In conclusion, the USPSTF reasoned that the additional benefit gained by starting screening at age 40 years rather than at age 50 years is small and that moderate harms from screening remain at any age. This leads to the C recommendation. The USPSTF notes that a "C" grade is a recommendation against routine screening of women aged 40-49 years. The Task Force encourages individualized, informed decision-making about when to start mammography screening.

Research Needs and Gaps

A series of randomized clinical trials that would compare the results of stopping breast cancer screening at different ages (by first comparing stopping screening at age 75 years with continued screening and then further comparing stopping screening at earlier ages, depending on the results of the first study) would be ethical and informative.

Extended follow-up of this type of study might also provide useful information about overdiagnosis in this age group. In general, more studies of overdiagnosis, including comparisons of lifetime breast cancer incidence among similar screened and unscreened women, would be helpful. Studies on overdiagnosis might also include long-term follow-up of women with probable missed cases of DCIS on the basis of microcalcifications that were missed in an earlier mammogram. Such studies could provide the percentage of these women who develop invasive breast cancer over the next 10 or more years.

Randomized clinical trials of film vs digital mammography among women with dense breast tissue, with sufficient follow-up to detect stage shifts (reductions of late-stage cancer) or decreases in clinical interval cases, would also be ethical and helpful.

Better understanding of certain facets of tumor biology is needed, particularly how age, race, breast density, and other factors may predispose certain women toward tumors with faster growth rates and greater lethality. This would improve the ability to determine at diagnosis which patients can be treated minimally.

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