Background
Although various radiographic modalities are readily available to identify lesions that are suspicious for breast cancer, mammography remains the mainstay of breast cancer screening. The role of breast sonography is confined mainly to the diagnostic follow-up of a mammographic abnormality because it may help clarify features of a potential lesion. The role of magnetic resonance imaging (MRI) for breast cancer screening is still evolving; currently MRI screening, in combination with mammography, is reserved for the screening of high-risk patients only. [1, 2, 3, 4]
In 2022, an estimated 290,560 new cases of invasive breast cancer are expected to be diagnosed—287,850 in women and 2710 in men—along with an estimated 51,400 cases of in situ breast cancer in women. Approximately 43,250 women and 530 men are expected to die from breast cancer in 2022. [1]
Incidence rates of invasive female breast cancer have been increasing by about 0.5% per year since the mid-2000s. In contrast, overall breast cancer death rates decreased 42% from 1989 to 2019, because of both improvement in treatments and earlier detection. [1]
The lifetime risk of a woman being diagnosed with breast cancer is 12.9%, or more than 1 in 8. [5] Due to the magnitude of the disease, its psychosocial impact, and associated morbidity and mortality, screening for early diagnosis forms a pivotal part of the struggle against this cancer.
According to the National Health Interview Survey, about 70% of women age 45 to 74 year have had a mammogram within the past 2 years. Breast cancer screening rates were higher in non-Hispanic white (71.7%) and non-Hispanic black (72.9%) women compared with non-Hispanic Asian (67.0%) and Hispanic (66.3%) women. [6]
According to the U.S. Preventive Services Task Force, the number of breast cancer deaths averted by screening and early treatment increases with age: over a 10-year period, screening 10,000 women aged 60-69 years will result in 21 fewer deaths from breast cancer; 8 fewer deaths in 10,000 women 50-59 years; and 3 fewer deaths in 10,000 women 40-49 years. [4]
Indications
In studies, mammography has clearly been shown to increase the detection of breast cancer at an earlier stage. [7] Based upon consistent data from multiple randomized trials, a strong consensus has been developed in favor of routine screening mammography for all women aged 50-69. Consensus, however, is not as strong in favor of routine screening among women aged 40-49 or women over the age of 70, and on how frequently these patient populations should be screened.
Based upon pooled data from 8 trials, the U. S. Preventive Services Task Force (USPSTF) has given an estimate that 1904 women aged 39-49 (95% credible interval [CrI], 929 to 6378 women) would need to be screened to prevent one death from breast cancer after at least 11 years of observation, compared with 1339 women in their 50s (CrI 322-7455) and 377 women in their 60s (CrI 230-1050). [8] Moreover, false-positive readings are more common in younger women, both because the tests are less specific and because breast cancer occurs less commonly in that population. [9, 10]
Recommendations for mammography by the American Cancer Society (ACS) include the following [2, 3] :
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Women with an average risk of breast cancer should undergo regular screening mammography starting at 45 years of age.
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Women 45-54 years of age should be screened annually.
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Women ≥55 years should transition to biennial screening or have the opportunity to continue screening annually.
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Women should have the opportunity to begin annual screening between the ages of 40 and 44 years.
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Women should continue screening mammography as long as their overall health is good and they have a life expectancy ≥10 years.
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The ACS does not recommend clinical breast examination for breast cancer screening among average-risk women at any age.
Recommendations for mammography by the USPSTF include the following [4] :
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The USPSTF recommends biennial screening mammography for women aged 50-74 years of age.
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The decision to start screening mammography in women prior to age 50 years should be an individual one.
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Women who place a higher value on the potential benefit than the potential harms may choose to begin biennial screening between the ages of 40 and 49 years.
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Current evidence is insufficient to assess the balance of benefits and harms of screening mammography in women aged 75 years or older.
A study of screening mammography beyond age 75 years, using data from the Surveillance, Epidemiology, and End Results (SEER) program and Breast Cancer Surveillance Consortium, concluded that although annual mammography is not cost-effective, biennial screening mammography to age 80 years is. The absolute number of deaths averted is small, however, especially for women with comorbidities. [11]
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Normal mammograms in a 40-year-old woman show dense breast parenchyma.
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Screening mammogram depicts malignant ductal-type microcalcifications.
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Image shows a malignant-type lesion: an invasive ductal carcinoma. This stellate (spiculated) lesion has ductal-type microcalcifications.
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Image shows a benign lesion: a fibroadenoma with well-defined edges and a halo sign.
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Benign microcalcifications: cystic hyperplasia.
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Breast cancer, mammography. Bilateral mammogram shows diffuse inflammatory carcinoma of the left breast.
