Is ultrasound recommended for breast cancer screening in women with dense breast tissue?

Ultrasound for Supplemental Screening in Dense Breasts

Ultrasound can be considered for supplemental breast cancer screening in women with dense breasts, particularly for average-risk women with heterogeneously dense tissue, though MRI is generally superior when accessible. 1

Risk-Stratified Approach to Supplemental Screening

The American College of Radiology recommends stratifying women by both breast density and overall breast cancer risk to determine the most appropriate supplemental screening modality. 1

Average-Risk Women with Dense Breasts

For average-risk women (lifetime risk <15%) with heterogeneously dense tissue, breast ultrasound may be appropriate as a supplemental screening option, though breast MRI or abbreviated MRI (AB-MRI) are also reasonable choices. 1

• Ultrasound detects an additional 0.3-7.7 cancers per 1000 examinations (median 4.2 cancers per 1000), with most being small invasive cancers. 1, 2
• The ACRIN 6666 trial demonstrated that adding ultrasound to mammography increased cancer detection from 7.6 to 11.8 per 1000 women screened (an increase of 4.2 cancers per 1000). 1
• Most cancers detected by supplemental ultrasound are small (mean size 9.9 mm), invasive, and 90% have negative lymph node status. 3

Intermediate-Risk Women with Dense Breasts

For intermediate-risk women (lifetime risk 15-20%) with heterogeneously or extremely dense tissue, breast MRI and AB-MRI are usually appropriate as first-line supplemental screening, while ultrasound and contrast-enhanced mammography (CEM) may be appropriate as alternatives. 1

High-Risk Women

For high-risk women (lifetime risk ≥20%), breast MRI or AB-MRI is usually appropriate regardless of breast density, with ultrasound or CEM considered only when MRI is contraindicated or unavailable. 1

Understanding the Trade-offs

Benefits of Ultrasound

• Detects additional early-stage invasive cancers not visible on mammography in dense breasts. 1, 4, 5
• No radiation exposure or intravenous contrast required. 5
• More accessible and less expensive than MRI. 5
• Can be performed by technologists using automated breast ultrasound (ABS), reducing operator dependence. 1, 6

Limitations and Harms

The major limitation is a substantial increase in false-positive biopsies: ultrasound reduces the positive predictive value (PPV) for biopsy from 22.6% for mammography alone to 11.2% for mammography plus ultrasound. 1

• Ultrasound generates an additional 11.7-106.6 biopsies per 1000 examinations (median 52.2), with PPV of only 8.4-13.7% for ultrasound-prompted biopsies. 2, 3
• This means approximately 276 biopsies are needed to detect 31 cancers when ultrasound is added. 1
• Requires significant additional interpretation time and trained personnel. 5

Why MRI is Generally Preferred When Available

Breast MRI demonstrates superior sensitivity (81-100%) compared to ultrasound and detects cancers that are smaller, lymph node negative, and less biologically aggressive. 1, 7

• Abbreviated MRI shows cancer detection rates of 15.2 per 1000 examinations compared to 6.2 per 1000 with digital breast tomosynthesis in dense breasts. 7
• MRI is the most effective supplemental modality for women with extremely dense breasts. 7

Critical Caveat About Evidence Quality

The U.S. Preventive Services Task Force states that current evidence is insufficient to recommend a specific screening strategy for women with dense breasts, as data do not yet demonstrate that supplemental screening reduces breast cancer mortality or improves quality of life. 7

• While supplemental ultrasound increases cancer detection rates, there is no proven mortality benefit. 7
• All supplemental screening modalities increase false-positive results, recalls, and biopsies. 7

Practical Implementation Algorithm

1. Assess overall breast cancer risk by age 25-30, especially for Black women and those of Ashkenazi Jewish descent. 1

2. For average-risk women with heterogeneously dense breasts:

   • First-line: Consider MRI or AB-MRI if accessible and affordable. 1
   • Alternative: Whole breast ultrasound (automated or handheld) is appropriate. 1, 6
   • Discuss trade-offs: increased cancer detection versus increased false-positive biopsies. 1, 7

3. For intermediate-risk women with dense breasts:

   • Strongly recommend MRI or AB-MRI as first-line. 1
   • Use ultrasound only if MRI is contraindicated or unavailable. 1

4. For high-risk women:

   • MRI is the standard of care regardless of density. 1
   • Ultrasound only if MRI cannot be performed. 1

Common Pitfalls to Avoid

• Do not assume all women with dense breasts need supplemental screening—risk stratification is essential. 1
• Do not use ultrasound as first-line supplemental screening in high-risk women—MRI is superior and recommended. 1
• Do not fail to counsel patients about the high false-positive rate (approximately 8-9 negative biopsies for every cancer detected). 1, 3
• Do not forget that digital breast tomosynthesis (DBT) improves screening sensitivity in all women and should be used as the baseline mammography technique when available. 1