When is a screening breast ultrasound recommended?

When is Screening Breast Ultrasound Recommended?

Screening breast ultrasound is recommended primarily as supplemental screening for women with dense breasts who have elevated breast cancer risk, or as an alternative when MRI is contraindicated or unavailable in high-risk women. 1, 2

Primary Indications for Screening Ultrasound

High-Risk Women Who Cannot Undergo MRI

• For high-risk women (lifetime risk ≥20%, BRCA mutations, or prior chest radiation) who qualify for but cannot tolerate MRI, ultrasound should be used as supplemental screening. 1, 3, 4
• This includes women with contraindications to MRI contrast, claustrophobia, or implanted devices incompatible with MRI. 1, 4
• However, MRI remains superior with 91-98% sensitivity compared to ultrasound, so MRI should always be attempted first in high-risk populations. 3, 2

Average-Risk Women with Dense Breasts

• For average-risk women with heterogeneously dense or extremely dense breast tissue on mammography, ultrasound may be considered as supplemental screening. 1, 2
• The decision must weigh the benefit of detecting an additional 0.3-7.7 cancers per 1,000 examinations against the substantial harm of 11.7-106.6 additional biopsies per 1,000 examinations, with a positive predictive value dropping from 22.6% to 11.2%. 2, 5
• This translates to approximately 8-9 negative biopsies for every cancer detected when ultrasound is added. 2

Intermediate-Risk Women with Dense Breasts

• For intermediate-risk women with dense breasts, ultrasound may be appropriate if MRI or abbreviated MRI is not accessible or affordable. 2
• MRI should be strongly recommended as first-line supplemental screening, with ultrasound reserved only when MRI cannot be performed. 2

When Screening Ultrasound is NOT Recommended

Average-Risk Women Without Dense Breasts

• Data regarding supplemental screening ultrasound in average-risk women with non-dense breasts is not compelling, with an incremental cancer detection rate of only 3.3 per 1,000 examinations. 1
• No methodologically sound evidence justifies routine use of ultrasound as an adjunct screening tool in women at average risk without dense breasts. 6

As Primary Screening Modality

• Ultrasound should never replace mammography as the primary screening modality, as it does not detect most microcalcifications, which are often the only sign of ductal carcinoma in situ. 4
• Mammography is the only screening modality with proven mortality reduction (20% relative reduction) in randomized controlled trials. 4

High-Risk Women Who Can Undergo MRI

• For high-risk women who can tolerate MRI, ultrasound should not be used as the supplemental screening modality. 1, 3, 2
• The European Society for Medical Oncology explicitly states there is no consensus for ultrasound use in screening, even for high-risk women with familial breast cancer. 3, 4

Critical Caveats and Common Pitfalls

Risk Stratification is Essential

• Do not assume all women with dense breasts need supplemental screening—overall breast cancer risk must be assessed using models like Tyrer-Cuzick, Gail, or BRCAPRO. 3, 2
• Women with extremely dense breasts have a 2.1-fold relative risk compared to average density, which some providers consider elevated beyond "average risk." 1

Patient Counseling Requirements

• Patients must be counseled about the high false-positive rate: approximately 98% of women recalled for positive ultrasound findings will not have cancer. 6
• The substantial increase in benign biopsies and associated anxiety, cost, and potential complications must be discussed. 2, 5

Limitations of Ultrasound

• Ultrasound has lower sensitivity than mammography for certain cancer types and cannot replace it. 4
• Interpretation time is operator-dependent, and automated whole-breast ultrasound may address some reproducibility concerns. 7, 8

Practical Implementation Algorithm

For women with dense breasts identified on mammography:

1. Assess overall breast cancer risk using validated models (Tyrer-Cuzick, Gail, family history). 3, 2

2. If lifetime risk ≥20% or high-risk criteria met:

   • First-line: Annual MRI + mammography starting age 25-30. 3, 2
   • If MRI contraindicated/unavailable: Use ultrasound as alternative. 1, 4

3. If intermediate risk with dense breasts:

   • Preferred: MRI or abbreviated MRI if accessible. 2
   • Alternative: Ultrasound if MRI not feasible. 2

4. If average risk with heterogeneously/extremely dense breasts:

   • Discuss risks vs. benefits of supplemental ultrasound. 2, 5
   • Consider MRI/abbreviated MRI as superior alternative if available. 2
   • If patient desires supplemental screening after counseling: Ultrasound is appropriate. 1, 2

5. If average risk without dense breasts:

   • Do not offer screening ultrasound. 1, 6