Breast cancer is the leading cause of premature death in women. According to the American Cancer Society (ACS), more than 40,000 US women will die of breast cancer in 2015. Previous studies have shown that breast cancer screening is associated with a reduction in breast cancer mortality. Therefore, improving access to high-quality breast cancer screening remains a priority in the United States.
However, the need to balance between the benefits and risks of mammography screening, and the age to begin screening and the appropriate screening interval, have long been topics of debate. In an effort to clarify these issues and shed some new light on this debate, the ACS embarked on a reevaluation of the current evidence with the goal of updating its 2003 guidelines for breast cancer screening for women at average risk for the disease. The updated guidelines were published in JAMA in October 2015 (Oeffinger KC, et al. JAMA. 2015;314:1599-1614).
As defined by the ACS, women at average risk for breast cancer are those who have:
- No personal history of breast cancer
- No suspected or confirmed genetic mutation
- No history of radiotherapy to the chest at a young age.
- The benefits and risks of mammography screening in average-risk women aged ≥40 years
- The benefits and risks of screening associated with different intervals (ie, annual, biennial, triennial) and how they vary by age
- The benefits and risks of clinical breast examination (CBE) among average-risk women aged ≥20 years.
Women Should Undergo Mammography Starting at Age 45 Years
Unlike the 2003 guidelines, which recommended that women start mammography screening at 40 years, the new guidelines increase the age of breast cancer screening to 45 years, because of the reduced burden of disease and the increased risk for adverse outcomes in younger women aged <45 years.
Otis W. Brawley, MD, FACP, Chief Medical Officer, American Cancer Society, and coauthor of the updated guidelines, said, "The number of cancer cases among women aged 40 to 44, and the difficulty in assessing a mammogram in this group, means that an individual woman is extremely unlikely to benefit from screening. Women of increased risk should be screened, even though mammography in this age group has extreme limitations and even harms."
Nevertheless, the ACS emphasizes that women can decide to undergo screening earlier than is recommended, and endorses discussing breast screening with women beginning at age 40 years. Furthermore, the ACS recommends that women aged 45 to 54 years undergo annual screening, whereas women aged ≥55 years should be screened biennially. Again, the new guidelines honor women's preferences, stating that individuals aged 40 to 44 years can choose annual screening.
In response to this recommendation, Priscilla Slanetz, MD, MPH, Radiologist, Beth Israel Deaconess Medical Center, predicts that women aged <45 years will continue to undergo annual mammography. "In reality, if the goal is to save the most lives, there is sufficient data to support annual mammography starting at age 40 years, and I suspect that most, if not nearly all, women will continue to choose this option when they are educated about the facts," Dr Slanetz said. "In addition, as younger women tend to develop more biologically aggressive breast cancers, more frequent screening, not less frequent, is the only way to save the most lives," she added.
Mammography Screening Should Continue for Women of Overall Good Health Whose Life Expectancy Is ≥10 Years
Because the incidence of breast cancer continues to increase until age 75 to 79 years, the updated guidelines recommend mammography for women of good health. This recommendation comes after reports from observational and modeling studies showing a reduction in breast cancer mortality in healthy women aged ≥75 years who underwent mammography screening. The ACS emphasizes that this recommendation pertains specifically to women who are free of serious comorbid conditions and who have a life expectancy of 10 years or longer. Currently, however, older women of poor health continue to undergo mammography testing, sometimes at the cost of increased anxiety, adverse effects of testing, and a risk for overdiagnosis.
Clinical Breast Examination Is Not Recommended for Screening in Women at Average Risk
Whereas the 2003 guidelines endorse periodic CBE for women aged <40 years and annual CBE for women aged >40 years, the 2015 guidelines do not recommend CBE for average-risk women of any age. This updated recommendation is based on findings indicating that CBE alone, or in combination with screening mammography, does not impart any benefit for detecting breast cancer in women at average risk. Furthermore, there is evidence that adding CBE to screening mammography results in an increase in the false-positive rate. However, the ACS stresses that CBE may be a valuable assessment tool in high-risk women, as well as in poorer regions, where mammography screening may not be easily accessible.
Mammography Screening: Challenges and Opportunities
The ACS emphasizes that mammography screening leaves plenty of room for improvement, especially because adherence to screening guidelines is not up to par. In addition, variability in the sensitivity and specificity of mammography hinders the accuracy of screening and could be improved with better training and education.
Dr Otis concluded that a better screening tool is needed, saying, "Most experts agree that the clinical trials that show a benefit for women age 40 to 49 shows about a 20% reduction in relative risk of death. This means mammography fails 80% of women this age who need a good screening test. One message often overlooked is 'We need to develop a better test for women!' "
In an accompanying editorial published in the same issue, Nancy L. Keating, MD, MPH, Department of Health Care Policy, Harvard Medical School and her colleague, said that the evidence supporting indisputable guidance for breast cancer screening remains incomplete (Keating NL, Pace LE.JAMA. 2015;314:1569-1571). For more information on this editorial, see the November issue of Value-Based Cancer Care.