Importance
Breast cancer is the second-leading cause of cancer death among women in the United States. Widespread use of screening, along with treatment advances in recent years, have been credited with significant reductions in breast cancer mortality.
Detection
Mammography, as well as physical examination of the breasts (CBE and BSE), can detect presymptomatic breast cancer. Because of its demonstrated effectiveness in randomized, controlled trials of screening, film mammography is the standard for detecting breast cancer; in 2002, the USPSTF found convincing evidence of its adequate sensitivity and specificity.
Benefits of Detection and Early Intervention
There is convincing evidence that screening with film mammography reduces breast cancer mortality, with a greater absolute reduction for women aged 50 to 74 years than for women aged 40 to 49 years. The strongest evidence for the greatest benefit is among women aged 60 to 69 years.
Among women 75 years or older, evidence of benefits of mammography is lacking.
Adequate evidence suggests that teaching BSE does not reduce breast cancer mortality.
The evidence for additional effects of CBE beyond mammography on breast cancer mortality is inadequate.
The evidence for benefits of digital mammography and MRI of the breast, as a substitute for film mammography, is also lacking.
Harms of Detection and Early Intervention
The harms resulting from screening for breast cancer include psychological harms, unnecessary imaging tests and biopsies in women without cancer, and inconvenience due to false-positive screening results. Furthermore, one must also consider the harms associated with treatment of cancer that would not become clinically apparent during a woman's lifetime (overdiagnosis), as well as the harms of unnecessary earlier treatment of breast cancer that would have become clinically apparent but would not have shortened a woman's life. Radiation exposure (from radiologic tests), although a minor concern, is also a consideration.
Adequate evidence suggests that the overall harms associated with mammography are moderate for every age group considered, although the main components of the harms shift over time. Although false-positive test results, overdiagnosis, and unnecessary earlier treatment are problems for all age groups, false-positive results are more common for women aged 40 to 49 years, whereas overdiagnosis is a greater concern for women in the older age groups.
There is adequate evidence that teaching BSE is associated with harms that are at least small. There is inadequate evidence concerning harms of CBE.
USPSTF Assessment
The USPSTF has reached the following conclusions:
For biennial screening mammography in women aged 40 to 49 years, there is moderate certainty that the net benefit is small. Although the USPSTF recognizes that the benefit of screening seems equivalent for women aged 40 to 49 years and 50 to 59 years, the incidence of breast cancer and the consequences differ. The USPSTF emphasizes the adverse consequences for most womenwho will not develop breast cancerand therefore use the number needed to screen to save 1 life as its metric. By this metric, the USPSTF concludes that there is moderate evidence that the net benefit is small for women aged 40 to 49 years.
For biennial screening mammography in women aged 50 to 74 years, there is moderate certainty that the net benefit is moderate.
For screening mammography in women 75 years or older, evidence is lacking and the balance of benefits and harms cannot be determined.
For the teaching of BSE, there is moderate certainty that the harms outweigh the benefits.
For CBE as a supplement to mammography, evidence is lacking and the balance of benefits and harms cannot be determined.
For digital mammography and MRI as a replacement for mammography, the evidence is lacking and the balance of benefits and harms cannot be determined.
