Breast cancer is common, but when viewed over a 10-year period, the risk for the average woman is relatively small. During the past few years, scientific controversy about the benefits of screening mammography has increased. As with most screening tests, there are hazards — primarily, risks of false positive mammograms, with associated anxiety and unnecessary biopsies, and perhaps a risk of overdiagnosis.
When the benefits of medical interventions are controversial and when hazards exist, shared decision making is needed, with the clinician providing facts and the patient assessing her situation from the vantage point of her personal values. In addition, the climate in the United States with regard to malpractice makes discussions between clinician and patient about breast-cancer screening essential for all women beginning at 40 years of age. To save time, information can be provided by handouts and an office practice that is organized to address the concerns of patients.
Women vary in terms of how much they want to participate in decisions about screening. In one survey of women younger than 50 years of age, 49 percent wanted to share in decision making, 44 percent wanted to make the decision themselves, and 7 percent wanted the physician to decide.5
However, 79 percent wanted information from the doctor. Because of varying individual values, and because women have a good deal of fear about breast cancer,53
physicians should be prepared for a decision different from the one they would recommend.
A woman needs some knowledge of her risk of breast cancer and the benefits and hazards of screening — specifically, her risks of the development of and death from breast cancer and her chances of successful treatment with screening and without screening, of having a false positive mammogram or an invasive breast procedure, and of having ductal carcinoma in situ diagnosed. Numerical risks may be best explained with the use of pictures or graphs, with discussion of absolute as well as relative risks (occurring over meaningful periods), and through comparisons with other risks.54
All women, regardless of age, should be asked whether they have a family history of breast cancer, ovarian cancer, or both ().55,56
For women without strong family histories, discussions about breast-cancer screening should begin at 40 years of age and continue until life expectancy is less than 10 years. Evidence supporting the usefulness of mammographic screening is strongest for women between 50 and 69 years of age, and screening should be routinely recommended for women in this age group. For women 40 to 49 years of age (such as the patient described in the vignette), shared decision making is especially important, because the absolute benefit of screening is smaller and the risks associated with it are greater. Screening should be routinely discussed, and the patient and clinician should decide together according to the woman's values.
Recommendations Regarding Breast-Cancer Screening in Women.
For women who want more information, , the Breast Cancer Risk Assessment Tool, or both can be used to estimate the individual risk of breast cancer. Women should be reminded that the risk of breast cancer increases with age and that the one-in-eight risk is a lifetime risk for a newborn who lives for 90 years.
The chances of being helped or harmed by screening mammography are summarized in and , which contain information that may be useful to patients. These figures show the chances that yearly screening mammography in women of different ages will result in a false positive mammogram, an invasive breast procedure, or a diagnosis of ductal carcinoma in situ or invasive breast cancer. Women should be made aware that at least half the patients given a diagnosis of breast cancer survive regardless of the use or nonuse of screening — a fact that many women do not understand.57,58
Recently, survival rates have been improving, but how much of this improvement is attributable to treatment itself and how much to earlier diagnosis due to screening are difficult to determine. The number of women “saved” is calculated according to the estimates that screening of women in their 40s reduces mortality from breast cancer by about 20 percent and screening of women in their 50s or 60s reduces it by about 30 percent. It should be emphasized that these numbers may vary, depending on the efficacy of mammography in reducing mortality. Individual women will interpret these numbers differently depending on their own values.
Chances of False Positive Mammograms, Need for Biopsies, and Development of Breast Cancer among 1000 Women Who Undergo Annual Mammography for 10 Years
Chances of Breast-Cancer–Related Outcomes among 1000 Women Who Undergo Annual Mammography for 10 Years
To decrease the risk of false positive results, patients should be referred to experienced mammographers with recall rates of no more than 10 percent. They should be encouraged to obtain previous mammograms for comparison and should undergo screening more frequently than every 18 months.
Women often are unaware of the difference between screening and diagnostic examinations to evaluate a breast symptom or abnormal finding. In one study, cancer was diagnosed in about 10 percent of women older than 40 years of age who reported a breast mass and in almost 5 percent of those with any breast-related problem.59
Clinicians and women should not be falsely reassured by a previously normal screening mammogram in the case of a new breast-related problem.