Breast Cancer Screening

Breast cancer is the most common cancer in women and the 2nd-leading cause of cancer-related deaths in women in the United States. Early detection and improved pathology-specific treatments have resulted in a decrease in death rates. Several organizations provide recommendations regarding screening for specific age and risk groups. Screenings include breast examination, mammography, magnetic resonance imaging (MRI), and ultrasound (US).

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Overview

Breast Cancer

Breast cancer is a disease characterized by malignant transformation of the epithelial cells of the breast.

Epidemiology

  • Breast cancer is the most common cancer in women.
  • Accounts for 29% of all malignant diseases among women in the United States
  • Incidence: 125 cases per 100,000 women
  • Risk increases with age, with 90% of cases occurring in women > 40 years of age
  • Male breast cancer accounts for < 1% of total cases.
  • An important cause of death in women:
    • United States: the 2nd-leading cause of cancer-related deaths
    • Developing countries: the leading cause of cancer-related deaths
  • Early detection and improved treatments have reduced death rates.

Risk factors

Unmodifiable factors that increase the risk:

  • Family history:
    • Breast cancer in 1st- or 2nd-degree relatives (mother, grandmother, sister)
    • Ashkenazi Jewish descent
  • Hormonal influences: long hormone exposure due to early menarche and/or late menopause
  • Genetic mutations (examples):
    • BRCA1 (on chromosome 17q)
    • BRCA2 (on chromosome 13q)
    • p53 (on chromosome 17)
  • Increasing age
  • Breast cancer on the contralateral side

Modifiable risk factors:

  • Lifestyle factors that increase the risk: 
    • High-fat diet
    • Obesity (especially after menopause)
    • Heavy alcohol use
    • Tobacco
  • Hormonal influences that increase the risk:
    • Higher age at 1st delivery (> 30 years of age)
    • Nulliparity
    • Hormone replacement therapy after menopause (> 5 years)
  • Hormonal influences that decrease the risk: breastfeeding for at least 6 months

Mnemonics:

BReast-CAncer 1 and 2” = Mutated genes are the BRCA1 and BRCA2 genes.

Initial risk assessment

Details of the patient’s medical and personal history are needed to determine their risk:

  • Personal and family history of breast, ovarian, tubal, or peritoneal cancer
  • Ancestry (associated with BRCA1 and 2)
  • Known carrier of a gene mutation for breast or ovarian cancer
  • Mammographic breast density
  • High-risk lesion on a previous breast biopsy
  • History of chest radiotherapy (age 10 to 30 years)

A patient’s risk for developing breast cancer can be classified as:

  • Average:
    • Have none of the above risk factors (most patients)
    • Lifetime risk < 15%
  • Moderate: 
    • Most women with a family history of breast cancer in a 1st-degree relative, but no known genetic syndrome
    • Lifetime risk 15%‒20%
  • High:
    • Patients with a known genetic predisposition, a personal history of breast cancer, or radiotherapy
    • Lifetime risk > 20%

Risk prediction models

Prediction models are utilized for specific categorization of risk, with more factors considered.

  • Breast cancer risk assessment tool (Gail model): 
    • The most commonly used risk model
    • Indicated for patients with no personal or strong family history of breast cancer 
    • Takes into account age, ethnicity, age of menarche, parity, and family history
    • Less precise for older women
    • Cannot be used in certain subgroups (such as patients with genetic mutations)
  • Other risk assessment models are used for patients with:
    • History of breast cancer or in situ breast cancer
    • Known mutation in the BRCA1 or 2 genes
    • Known or suspected inherited syndrome (linked with breast cancer)

Strategies for Screening

Breast examination

  • Self-examination: 
    • Generally discouraged
    • Can lead to unnecessary procedures (e.g., mammograms and biopsies)
  • Clinical examination:
    • Generally not recommended for average-risk women (adjunct only)
    • Utilized in the case of:
      • Women with a high risk (initial age differs depending on risk factors)
      • Any breast complaints or abnormalities
      • Low-resource settings
  • Localizing breast lesions:
    • If there is a vague or large area, then the area may be localized by a quadrant.
    • If there is a focal area, then the area will be localized by the clock face position and distance from the nipple.

Mammography

Mammography is the most effective method of detecting early breast cancer, consistently demonstrating a 20%–40% decrease in mortality among screened women:

  • High false-negative rate:
    • May miss an average of 20% of breast cancers
    • If there is clinical suspicion for malignancy, a negative mammogram does not rule out cancer, and further investigation is warranted.
  • Types:
    • Screen film mammography: mostly replaced by digital mammography in the United States
    • Digital mammography: preferred for dense breasts (approximately 50% of all women)
    • Digital breast tomosynthesis (BDT, “3-D mammography”):
      • Takes images from many angles to obtain a 3-dimensional picture
      • Improves the sensitivity and specificity of mammography
      • Preferred modality by the American College of Breast Surgeons
    • Computer-aided detection (CAD) often used: an artificial intelligence (AI) technique that uses pattern recognition to highlight suspicious features and marks the features for the radiologist to review; CAD decreases oversights 
  • The breast imaging reporting and data system (BI-RADS):
    • Standardizes the mammography report
    • Indicates categories and corresponding recommendations 
  • Screening versus diagnostic mammograms:
    • Screening mammogram: performed on a woman with no symptoms or signs of breast cancer
    • Diagnostic mammogram: performed on a woman who has a breast lesion suspicious for cancer either on clinical grounds or by findings on a screening mammogram
Table: Mammography findings and recommendations
CategoryAssessmentFollow-up
BI-RADS 0Incomplete assessmentAdditional mammography views or ultrasound follow-up needed
BI-RADS 1NegativeContinue with routine screening.
BI-RADS 2Benign findingsContinue with routine screening.
BI-RADS 3Probably benign findingsDiagnostic mammography or ultrasound in 6 months
BI-RADS 4Suspicious abnormalityBiopsy should be considered.
BI-RADS 5Highly suggestive of malignancyBiopsy should be performed.
BI-RADS 6Biopsy-proven malignancyManagement for breast cancer
Note: A negative report should not rule out malignancy if there is a high clinical suspicion. Consider ultrasound follow-up.

Magnetic resonance imaging (MRI)

  • Indicated as supplementary screening along with mammography in women with a high risk of breast cancer:
    • BRCA1 or 2 mutations
    • Strong family histories of breast and/or ovarian cancer
    • History of mantle radiation for Hodgkin’s lymphoma
  • Used to follow up an abnormal or inconclusive mammogram result
  • Higher false-positive rates in women with dense breasts, leading to unneeded biopsies
  • Despite the increased sensitivity for malignancy, there is no evidence of a decreased mortality benefit.

Mammography and breast MRI
Image A shows mammography of the left breast in a BRCA1 gene mutation carrier. Note the extremely dense breast tissue.
Image B demonstrates an MRI with an enhancing mass (arrow) in the upper left breast that was occult on the mammogram.

Image: “MRI for breast cancer: Current indications” by Ojeda-Fournier H, Comstock CE. License: CC BY 2.0.

Ultrasound (US)

  • Not routinely used for screening due to a high false-positive rate
  • Primarily used for diagnostic follow-up of an abnormal mammogram
  • Can be considered as an adjunct in patients with dense breasts

Screening for Average- and Moderate-risk Individuals

Average risk

Society and government-sponsored guidelines differ in:

  • The recommended age to start regular mammograms
  • Frequency of mammograms (annually or biennially)
  • Discontinuation of screening
Table: Breast cancer screening guidelines for average-risk individuals
OrganizationMammographyClinical breast examination
USPSTF
  • Age 40–49: individualize*
  • Age 50–74: every 2 years
  • Age > 75: insufficient evidence
Insufficient evidence
ACP
  • Age 40–49: individualize*
  • Age 50–74: every 2 years
  • Age ≥ 75: Discontinue screening if life expectancy is < 10 years.
Not recommended
ACS
  • May offer at age 40; start at age 45.
  • Age 45–54: annually
  • Age 55 and above: every 1–2 years
  • Continue if life expectancy is ≥ 10 years.
Not recommended
ACOG
  • May offer at age 40.
  • Start no later than age 50: every 1–2 years.
  • Age > 75: Assess health, longevity, and discontinuation options.
  • Age 29–39: every 1–3 years
  • Age ≥ 40: annually
NCCN
  • Age ≥ 40: annually
  • Age 20–39: every 1–3 years
  • Age ≥ 40: annually
*Discuss breast cancer screening, risks, benefits, and potential for unnecessary procedures. For patients who choose to initiate screening, mammography is performed every 1‒2 years.
ACOG: American College of Obstetricians and Gynecologists
ACP: American College of Physicians
ACS: American Cancer Society
NCCN: National Comprehensive Cancer Network
USPSTF: U.S. Preventive Services Task Force

Moderate risk

  • A similar approach to average-risk patients
  • Supplemental screening with MRI or US can be offered on a case-by-case basis.

Screening for High-risk Individuals

Screening and genetic testing

Recommendations:

  • Clinical breast exam: every 6–12 months by age 25 years (initiation and frequency depend on risk)
  • Annual mammogram (starts at age 30) and MRI (starts at age 25): for patients with BRCA1 or 2 mutations 
  • Annual mammogram and MRI generally start at age 30:
    • 1st-degree relative with known BRCA1 or 2 mutations
    • > 20% lifetime risk of breast cancer
    • Patients with radiation therapy to the chest at 10–30 years of age
    • Most high-risk syndromes
  • An annual mammogram for other high-risk women (e.g., personal history of in situ lesions, atypical ductal hyperplasia), with MRI discussed with a clinician

Genetic counseling and testing (USPSTF):

  • Familial risk assessment tools are recommended for women with the following:
    • A personal or family history of breast, ovarian, tubal, or peritoneal cancer
    • Ancestry associated with BRCA1 or 2 mutations
  • Familial risk assessment tools include:
    • Ontario family history risk assessment tool
    • Manchester scoring system
    • Referral screening tool
    • Pedigree assessment tool
    • 7-question family history screen
    • International breast cancer intervention study model
    • BRCAPRO (calculates the probability of carrying BRCA1 and/or BRCA2 mutation)
  • Positive results should lead to genetic counseling and potential genetic testing.
  • For women without a personal or family history or ancestry associated with BRCA1 or 2: genetic counseling and testing are not recommended.

Risk reduction

Non-surgical

  • Target modifiable risk factors:
    • Regular physical exercise
    • Weight loss
    • Decrease alcohol consumption
    • Smoking cessation
    • There is no evidence that dietary changes reduce risk.
  • Chemoprevention:
    • USPSTF: Risk-reducing medications recommended for high-risk women age ≥ 35 years (for a total of 5 years).
    • Considered in women at a high risk of breast cancer
    • Tamoxifen:
      • Selective estrogen receptor modulator
      • Indicated for BRCA2 carriers who opt out of prophylactic mastectomy 
      • Less effective than risk-reducing surgery
      • Used in pre- or postmenopausal women
    • Anastrozole:
      • Aromatase inhibitor
      • Used in postmenopausal women

Surgical: Prophylactic mastectomy

Women should be counseled on the potential morbidity of surgical procedures (surgical menopause, libido, body image).

  • Indications:
    • BRCA1 or BRCA2 carriers
    • Other genetic mutations that carry a greater lifetime risk for developing breast cancer
  • Does not completely eliminate the risk of cancer
  • May be done in conjunction with salpingo-oophorectomy to reduce ovarian cancer risk

Screening for Special Populations

Patients with dense breast tissue

  • The same approach to screening is recommended.
  • Digital mammography is preferred over film.
  • If there are no additional risk factors, no supplemental screening is recommended.
  • MRI or US may be used as an adjunct in moderate- or high-risk patients.

Male BRCA carriers

Male BRCA carriers have a higher risk for breast, prostate, and pancreatic cancers:

  • Monthly breast self-examination starting at age 35
  • Annual clinical breast exam starting at age 35
  • Annual mammography can be considered in men with gynecomastia or increased breast density (evidence is limited).
  • Prostate cancer screening starting at age 40 for BRCA2 carriers
  • Consideration of prostate screening starting at age 40 for BRCA1 carriers
  • Patients with breast implants:
    • Make mammography difficult (radiopaque content)
    • Involves 4 views (instead of the usual 2 views per breast)

References

  1. American Cancer Society. (2020). American Cancer Society recommendations for the early detection of breast cancer. https://www.cancer.org/cancer/breast-cancer/screening-tests-and-early-detection/american-cancer-society-recommendations-for-the-early-detection-of-breast-cancer.html
  2. Elmore, J.G., & Lee, C.I. (2020). Screening for breast cancer: Strategies and recommendations. UpToDate. Retrieved December 14, 2020, from https://www.uptodate.com/contents/screening-for-breast-cancer-strategies-and-recommendations
  3. Venkataraman, S., & Slanetz, P.J. (2020). Breast imaging for cancer screening: Mammography and ultrasonography. UpToDate. Retrieved December 14, 2020, from https://www.uptodate.com/contents/breast-imaging-for-cancer-screening-mammography-and-ultrasonography
  4. Elmore, J.G., & Lee, C.I. (2020). Screening for breast cancer: Evidence for effectiveness and harms. UpToDate. Retrieved December 14, 2020, from https://www.uptodate.com/contents/screening-for-breast-cancer-evidence-for-effectiveness-and-harms
  5. Freer, P.E., & Slanetz, P.J. (2020). Breast density and screening for breast cancer. UpToDate. Retrieved December 14, 2020, from https://www.uptodate.com/contents/breast-density-and-screening-for-breast-cancer
  6. Isaacs, C., & Peshkin, B.N. (2020). Cancer risks and management of BRCA1/2 carriers without cancer. UpToDate. Retrieved December 14, 2020, from https://www.uptodate.com/contents/cancer-risks-and-management-of-brca1-2-carriers-without-cancer
  7. Peshkin, B.N., & Isaacs, C. (2020). Genetic testing and management of individuals at risk of hereditary breast and ovarian cancer syndromes. UpToDate. Retrieved December 14, 2020, from https://www.uptodate.com/contents/genetic-testing-and-management-of-individuals-at-risk-of-hereditary-breast-and-ovarian-cancer-syndromes
  8. Viera, A.J. (2020). Overview of preventative care in adults. UpToDate. Retrieved December 14, 2020, from https://www.uptodate.com/contents/overview-of-preventive-care-in-adults
  9. Sharma, P., & Chen, W.Y. (2020). Selective estrogen receptor modulators and aromatase inhibitors for breast cancer prevention. UpToDate. Retrieved December 15, 2020, from https://www.uptodate.com/contents/selective-estrogen-receptor-modulators-and-aromatase-inhibitors-for-breast-cancer-prevention
  10. Kosir, M.A. (2020). Breast cancer. MSD Manual Professional Version. https://www.msdmanuals.com/professional/gynecology-and-obstetrics/breast-disorders/breast-cancer
  11. Newton, E.V., & Grethlein, S.J. (2020). Breast cancer screening. Medscape. https://emedicine.medscape.com/article/1945498-overview
  12. U.S. Preventive Services Task Force. (2016). Screening for breast cancer: U.S. Preventive Services Task Force recommendation statement. Annals of Internal Medicine. 2016(164), 279–96. 
  13. U.S. Preventive Services Task Force. (2019). Risk assessment, genetic counseling, and genetic testing for BRCA-related cancer. JAMA. 322(7), 652–65.
  14. American Society of Breast Surgeons. (2019). Position Statement on Screening Mammography. https://www.breastsurgeons.org/docs/statements/Position-Statement-on-Screening-Mammography.pdf
  15. Ibrahim, M., Yadav, S., Ogunleye, F., & Zakalik, D. (2018). Male BRCA mutation carriers: Clinical characteristics and cancer spectrum. BMC Cancer, 18. https://doi.org/10.1186/s12885-018-4098-y
  16. Isaacs, C., & Peshkin, B.N. (2020). UpToDate. Retrieved January 13, 2021, from https://www.uptodate.com/contents/cancer-risks-and-management-of-brca1-2-carriers-without-cancer
  17. Katzen, J., & Dodelzon, K. (2018). A review of computer aided detection in mammography. Clinical Imaging, 52, 305–309. https://doi.org/10.1016/j.clinimag.2018.08.014

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