Breast cancer risk assessment and screening

December 7, 2018

An examination of ACOG’s updated guidelines on breast cancer screening recommendations for the average-risk woman.

Assessment and Screening in Average-Risk Women. American College of Obstetricians and Gynecologists. Obstet Gynecol 2017;130:e1-16. Full text of Practice Bulletin #179 is available to ACOG members here.


BREAST CANCER RISK ASSESSMENT AND SCREENING IN AVERAGE-RISK WOMENBreast cancer is the most commonly diagnosed cancer in women in the United States and the second leading cause of cancer death in American women1. Regular screening mammography starting at age 40 years reduces breast cancer mortality in average-risk women2. Screening, however, also exposes women to harm through false-positive test results and overdiagnosis of biologically indolent lesions. Differences in balancing benefits and harms have led to differences among major guidelines about what age to start, what age to stop, and how frequently to recommend mammography screening in average-risk women2–4

Breast cancer risk assessment is very important for identifying women who may benefit from more intensive breast cancer surveillance; however, there is no standardized approach to office-based breast cancer risk assessment in the United States. This can lead to missed opportunities to identify women at high risk of breast cancer and may result in applying average-risk screening recommendations to high-risk women. Risk assessment and identification of women at high risk allow for referral to health care providers with expertise in cancer genetics counseling and testing for breast cancer-related germline mutations (eg, BRCA), patient counseling about risk-reduction options, and cascade testing to identify family members who also may be at increased risk. 

The purpose of this Practice Bulletin is to discuss breast cancer risk assessment, review breast cancer screening guidelines in average-risk women, and outline some of the controversies
surrounding breast cancer screening. It will present recommendations for using a framework of shared decision making to assist women in balancing their personal values regarding benefits and harms of screening at various ages and intervals to make personal screening choices from within a range of reasonable options. Recommendations for women at elevated risk and discussion of new technologies, such as tomosynthesis, are beyond the scope of this document and are addressed in other publications of the American College of Obstetricians and Gynecologists (ACOG)5–7.

Used with permission. Copyright the American College of Obstetricians and Gynecologists.

Changing guidelines

by Ilana Cass, MD


In 2009, the U.S. Preventative Services Task Force (USPSTF) updated their 2002 recommendations for breast cancer screening for average-risk women, based upon a systematic evidence review and decision analysis modeling, to lengthen the screening interval and accelerate the ending age of mammography.1 These guidelines were affirmed in 2016.2 In 2015, the American Cancer Society issued an update of its 2003 screening mammography guidelines to reflect new evidence from long-term follow-up of population-based screening programs.3 Both of these updates departed significantly from prior screening guidelines by advocating for a later age to start screening, age-dependent screening intervals, and no longer recommending periodic clinical breast exams or self-breast exams in combination with mammography as effective screening tools. 

Interpretation of these guidelines, based upon a reasonable balance of the associated benefits and harm, has led to variation in major expert opinions and guidelines regarding breast cancer screening for average risk women. Differences between these guidelines, notably the ages to start and end screening, as well as the optimal interval between screening, has created challenges for both patients and providers in choosing the most appropriate approach to screening. 

In Practice Bulletin #179 published July 2017, which replaces #122, ACOG addresses some of the controversy surrounding optimal breast cancer screening for average risk women.4 ACOG confirms the benefit of screening mammography to reduce breast-cancer associated mortality and the need for advanced cancer treatment, while acknowledging the potential associated adverse consequences, including false-
positive test results, anxiety/discomfort, overdiagnosis and overtreatment, and radiation exposure.4 These guidelines emphasize the importance of shared decision-making to allow patients to take an informed and active role in their health care.  

ACOG encourages physicians to use the clinical encounter as an opportunity to educate a patient about breast cancer risks and prevention, to elicit her family and medical risk, and to periodically determine if the patient’s risk factor profile has changed. ACOG recognizes that there is no single standardized model to assess breast cancer risk.  Women who are identified as having potentially increased breast cancer risk, based upon a combination of family or personal cancer history, demographic characteristics, reproductive history or hormonal exposure, and breast disorders, merit additional risk assessment using several validated tools outlined in Practice Bulletin #179. 

Shared decision-making involves candid dialogue between doctor and patient to elicit the patient’s values, goals of care, and perception of risk. To facilitate this discussion, Practice Bulletin #179 highlights the lifetime benefits and harms associated with commencing breast cancer screening in average-risk women at age 40 versus 50, and those associated with different screening intervals. Specifically, Tables 3 and 4 provide practical data on important considerations such as false-positive test results and unnecessary breast biopsies and balance these against life-years gained and disease-specific mortality to help guide decision making. 

Breast self-awareness and clinical breast exam

The updated ACOG guidelines do not recommend breast self-examination in average-risk women based upon an unfavorable harm/benefit ratio.  Breast self-awareness in average-risk women is endorsed by ACOG based upon the evidence that most breast cancers are detected by women themselves. ACOG encourages education about the signs and symptoms of breast cancer so women are alerted to changes in their breasts that require evaluation. ACOG suggests that the clinical breast exam may be offered to asymptomatic, average-risk women starting at age 25 until age 39 every 1 to 3 years and annually thereafter, despite the controversy over whether the small gain in enhanced detection of breast cancers results in improved patient outcomes. The clinical breast exam remains an important part of the evaluation for symptomatic or high-risk women.

Age to stop breast cancer screening

Some guidelines endorse screening until age 75. The utility of breast cancer screening for women over age 75 is limited based upon lack of data. This is a significant omission given that the average 75-year-old woman in the United States in 2018 is expected to live over 12 additional years.5 Amidst the controversy surrounding when to cease breast cancer screening, ACOG asserts that age alone should not be the basis for decisions regarding discontinuation of screening mammography. Practice Bulletin #179 suggests that shared decision-making and a general health assessment using clinical judgement and predictive models are the best tools to inform decisions about breast cancer screening. ACOG states that screening mammography is not appropriate for women who would not choose further evaluation of abnormal results.  

Trends in breast cancer screening 

Despite recent changes in breast cancer screening guidelines, there has been minimal impact on the interval or use of breast cancer screening.6,7 A cohort study of 12 million Medicare fee-for-service women aged 65 or older found no significant decrease in frequency of mammograms between 2007-2009 (before) and 2010-2012 (after) despite the 2009 USPSTF recommendations for biennial, rather than annual, mammogram screening and to discontinue screening at age 75.6 Another prospective study of women aged 40 to 74 who received screening mammograms between 2006 and 2012 using data from the Breast Cancer Surveillance Consortium reported no change in the intervals between mammograms following the 2009 USPSTF guidelines for any age group.7 The authors of both studies concluded that the lack of change may reflect patient choice and conflicting recommendations from clinicians. Further study is needed to evaluate the impact of the 2015 American Cancer Society guidelines on screening mammography, and patient perceptions of the guideline changes. In the interim, ACOG Practice Bulletin #179 offers a pathway to promote informed decision-making to align providers and patients to improve compliance with breast cancer screening recommendations.



The author reports no potential conflicts of interest with regard to this article.



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