On October 20, 2015, the American Cancer Society updated its guidelines for breast cancer screening in the United States.
Published in the Journal of the American Medical Association (JAMA), the new guidelines come amidst staggering statistics: 231,840 women will be diagnosed with breast cancer in 2015, a disease second only to lung cancer as the leading cause of death for American women.
The guidelines were developed by a group of professionals that included clinicians, biostatisticians, an epidemiologist, and an economist. Importantly, the guidelines are designed for women at average risk of breast cancer and reflect a shift toward the recommendations released by the US Preventative Services Task Force (USPSTF) in December 2009, those recommendations including bi-annual screening for women ages 50 to 74 and individualized decision making as to bi-annual screening for women between the ages of 40 and 49.
The most important changes to the ACS guidelines include the decision to move the recommendation for annual screening from age 40 to age 45 and a recommendation against clinical breast examinations.
Three key questions guided the drafters of the new guidelines:
- What are the relative benefits, limitations, and harms associated with mammography screening compared with no screening in average risk women 40 years and older, and how do they vary by age, screening interval, and prior screening history?
- Among average risk women who are screened with mammography, what are the relative benefits, limitations and harms associated with annual, bi-annual, tri-annual, or other screening interval, and how do they vary by age?
- What are the benefits, limitations, and harms associated with clinical breast examination (CBE) among average risk women 20 years and older compared with no CBE, and how do they vary by age, interval and participation rates and mammography screening?
The new guidelines reflect the development group’s judgement about when the benefits of mammography screening clearly or likely outweigh the potential harm to women at average risk of breast cancer. The recommendations are as follows:
- Recommendation 1. Women who have an average risk of breast cancer (the majority of women) – should begin yearly mammograms at age 45;
- Recommendation 1a. Women age 45 to 54 should be screened annually
- Recommendation 1b. Women 55 years and older should transition to bi-annual screening or have the opportunity to continue screening annually
- Recommendation 1c. Women should have the opportunity to begin annual screening between the ages of 40 and 44 years;
- Recommendation 2. Women should consider screening mammography as long as their overall health is good and they have a life expectancy of 10 years or longer;
- Recommendation 3. Clinical breast examination is not recommended for breast cancer screening in women of average risk at any age. Likewise, self-breast exams are no longer recommended.
According to the article, the purpose of the new guidelines is to “provide both guidance and flexibility for women about when to start and stop screening mammography and how frequently to be screened for breast cancer.” Likewise, an essential theme is how to strike the balance between the benefits and harms of breast cancer screening in light of individual preferences and risk tolerance.
A significant change from previous ACS guidelines published in 2003 was the withdrawal of the direct recommendation to begin screening at age 40. The article states the “lesser, but not insignificant, burden” of breast cancer for women between the ages of 40 and 44, combined with the higher cumulative risk of adverse outcomes, no longer warranted the direct recommendation” that screening begin at age 40.
The new guidelines were based in part on a thorough evidence review titled Benefits and Harms of Breast Cancer Screening. The evidence review, published in the same October 2015 edition of JAMA, concludes breast cancer screening reduces breast cancer mortality by approximately 20% among women of all ages. It also discusses the potential harms of breast cancer screening, including false-positives, overdiagnosis, and to a lesser extent, the threat of distress and anxiety associated with the diagnosis of cancer.
Notably, the evidence review cites the major potential harm of overdiagnosis as subject to a “high degree of uncertainty.” In addition, the review cited other studies which found anxiety related to false positive test results was transient only, and with no measurable health detriment.
Contrast these potential harms with a study cited in the review which estimated 600 lifetime cumulative deaths were prevented per 100,000 women when biannual screening starts at age 40 and 800 deaths prevented with annual screening. The same study found the benefits of screening on annual basis are more profound for younger women.
Consider also that the rate of false positive biopsies for women age 40-49 is just 1.5% higher than that for women age 50-59 (16.6 v. 15.1).
Throughout the evidence review the authors cite “uncertainty” about both the benefits and the harms associated with different breast cancer screening strategies. In light of the uncertainty regarding early breast cancer screening and the nature of the potential harms, we are troubled by the conclusion that the harms associated with annual screening before age 45 outweigh the benefit to thousands of woman whose lives would be saved if screening was recommended at age 40.
Certainly some potential harm exists in overdiagnosis and unnecessary treatment of early breast cancers which, if not diagnosed, would have no detrimental effects for many years, if any. However, and as recognized by the National Cancer Institute, there is no reliable way to distinguish between cancers which will become symptomatic or life-threatening and those which will not. It is this uncertainty which in our opinion creates the illusion of a choice from an individual perspective.
We believe the vast majority of women would prefer early detection and treatment rather than challenge the odds of having an undetected early breast lesion that will evolve into harmful disease. A discussion of the benefits and harms in the decision to undergo early screening seems misplaced and offers no true guidance where the future of a precursor lesion is itself so uncertain. Instead, the guiding principle in any discussion about early breast cancer screening should be that early screening saves live.
Even the writers of the new guidelines recognize the value of breast cancer screening is an issue that is contentious and debated in both the academic literature and the media. Rather than focusing on this debate, the writers recommend the discussion shift to how to increase exposure to and accuracy of testing. The thrust of the effort should be toward assuring more women adhere to recommended screening guidelines and providing better training, stronger standards and continuing education and feedback on the performance of mammography.
For a more in-depth discussion of the debate surrounding breast cancer screening and how some women weigh the benefits and harms, see the post Breast Cancer Screening and Mammography.