Reference: JAMA Netw Open. 2023 Apr 3;6(4):e238893
Practice Point: Black women have significantly higher risk for breast cancer mortality and would likely benefit from mammography screening starting at age 40. For other women, the data is less clear.
EBM Pearl: When considering the “average” risk of a disease in a population, remember that risk in distinct subpopulations may vary widely.
Screening recommendations for breast cancer in women of average risk have been the subject of much controversy over the years. Mammography decreases breast cancer-specific mortality for women aged 50-79, and most guidelines recommend mammography screening for women aged 50-74 every 1-2 years. That part is pretty clear. But for women aged 40-49 there is much uncertainty about the benefits and harms. Sadly, robust data has been lacking. As a result, recommendations from various guideline groups differ significantly, some recommending starting as early as age 40, others at age 50, and some in between. All include some degree of shared decision making. In 2016, the United States Preventive Services Task Force (USPSTF) recommended against routine screening for women aged 40-49, but recommended screening every 2 years if requested by an informed patient. However, a new draft proposal by this group recommends all women start screening at age 40. Why the fairly drastic change?
Recent data suggests that the risk of breast cancer is not the same across various racial and ethnic groups. An article in JAMA Network Open examined breast cancer rates among 5 groupings of women: White women, Black women, American Indian/Alaskan Native women, Hispanic women, and Asian/Pacific Islander women. While breast cancer mortality is decreasing in general, for 40-49 year olds annual mortality was 27/100,000 for Black women, 15 for White women, and around 11 for the 3 remaining groups mentioned above. Specifically, a 42-year-old Black woman has the same chance of dying from breast cancer over the next 10 years as a 51-year-old White woman, a 57-year-old American Indian/Alaska Native or Hispanic woman, or a 61-year-old Asian or Pacific Islander woman. Waiting until age 50 to start mammography screening in Black women may be part of the reason Black women have higher breast cancer mortality despite higher rates of screening. This indicates that Black women may benefit from initiating screening at age 40.
Soon after the JAMA article was published, the USPSTF released the draft of the update to their breast cancer screening guidelines (this was not likely informed by the JAMA article). If the draft does not undergo significant changes, they will be issuing a B recommendation for biennial screening of all 40-74 year-old women. The B recommendation means either a high certainty of moderate net benefit or moderate certainty of moderate-to-substantial net benefit. One of the things often ignored in debates over screening for cancer are the harms associated with screening. False positive test results and overdiagnosis are two obvious downsides to increased screening. (Overdiagnosis refers to cancers which are diagnosed but would not have become clinically evident in the absence of screening.) Some estimates for the rate of overdiagnosis from mammographic screening are as high as 15%! Clearly, this is an area for ongoing shared decision making. While it may make sense to start screening at age 40 for women at increased risk and it appears Black women should be considered at increased risk, whether this applies to all women remains to be seen.
For more information, see the topic Risk Factors for Breast Cancer in DynaMed.
DynaMed EBM Focus Editorial Team
This EBM Focus was written by Alan Ehrlich, MD, Executive Editor at DynaMed and Associate Professor in Family Medicine at the University of Massachusetts Medical School. Edited by Katharine DeGeorge, MD, MS, Deputy Editor at DynaMed and Associate Professor of Family Medicine at the University of Virginia; Dan Randall, MD, Deputy Editor at DynaMed; Nicole Jensen, MD, Family Physician at WholeHealth Medical; Vincent Lemaitre, PhD, Senior Medical Writer at DynaMed; Elham Razmpoosh, PhD, Postdoctoral fellow at McMaster University; and Sarah Hill, MSc, Associate Editor at DynaMed.