Ultrasound for Supplemental Screening in Dense Breasts

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, 2
• For average-risk women 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, 2, 3

Benefits and Limitations of Ultrasound

• Ultrasound detects an additional 0.3-7.7 cancers per 1000 examinations, with most being small invasive cancers 4
• The ACRIN 6666 trial demonstrated that adding ultrasound to mammography increased cancer detection from 7.6 to 11.8 per 1000 women screened 4
• The major limitation of ultrasound is a substantial increase in false-positive biopsies, reducing the positive predictive value (PPV) for biopsy from 22.6% for mammography alone to 11.2% for mammography plus ultrasound 4
• Approximately 276 biopsies are needed to detect 31 cancers when ultrasound is added 4

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, 5
• 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 5

Practical Implementation Algorithm

• For average-risk women with heterogeneously dense breasts, consider MRI or AB-MRI if accessible and affordable, or whole breast ultrasound as an alternative 1, 2
• For intermediate-risk women with dense breasts, strongly recommend MRI or AB-MRI as first-line, and use ultrasound only if MRI is contraindicated or unavailable 1, 2
• For high-risk women, MRI is the standard of care regardless of density, and ultrasound should only be used if MRI cannot be performed 1, 2, 6

Common Pitfalls to Avoid

• Do not assume all women with dense breasts need supplemental screening—risk stratification is essential 1, 2
• Do not use ultrasound as first-line supplemental screening in high-risk women—MRI is superior and recommended 1, 6
• Do not fail to counsel patients about the high false-positive rate of ultrasound, approximately 8-9 negative biopsies for every cancer detected 4

Screening Breast Ultrasound Recommendations

Primary Indications for Screening Ultrasound

• For high-risk women who qualify for but cannot tolerate MRI, the American College of Radiology recommends ultrasound as supplemental screening, including those with contraindications to MRI contrast, claustrophobia, or implanted devices incompatible with MRI 7
• The American College of Radiology suggests that for average-risk women with heterogeneously dense or extremely dense breast tissue on mammography, ultrasound may be considered as supplemental screening, weighing the benefit of detecting additional cancers against the harm of additional biopsies 8, 7

When Screening Ultrasound is NOT Recommended

• The American College of Radiology states that 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 8
• The American College of Radiology recommends that 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 8

Practical Implementation Algorithm

• For women with dense breasts identified on mammography, the American College of Radiology recommends assessing overall breast cancer risk using validated models, and if lifetime risk ≥20% or high-risk criteria are met, using annual MRI + mammography as first-line, or ultrasound as an alternative if MRI is contraindicated or unavailable 7
• For average-risk women with heterogeneously or extremely dense breasts, the American College of Radiology suggests discussing risks vs. benefits of supplemental ultrasound and considering MRI or abbreviated MRI as a superior alternative if available 8, 7

Breast Cancer Screening Recommendations for Women with Dense Breasts

Understanding the Clinical Impact of Breast Density

• Women with extremely dense breasts have a relative risk of 2.1 for developing breast cancer compared to those with average density, and those with heterogeneously dense breasts have a risk of 1.2, according to the American College of Radiology 9, 10, 11

Screening Algorithm Based on Density and Risk

• The American College of Radiology recommends that all women with dense breasts continue annual mammography screening starting at age 40, as mammography remains effective in reducing mortality even in these patients 9, 10
• For women with extremely dense breasts, the American College of Radiology strongly recommends MRI screening, which has been shown to reduce interval cancer rates, with a detection rate of 16.5 cancers per 1000 exams 9, 10, 11
• The European Society of Breast Imaging recommends MRI screening every 2-4 years for women aged 50-70 with extremely dense breasts 10, 11

Choosing the Appropriate Supplemental Modality

• MRI with contrast is the standard modality for women at high risk (≥20% lifetime risk) with dense breasts, regardless of density 9
• MRI screening has a sensitivity of 81-100%, superior to all other modalities, and detects smaller, less aggressive cancers 12, 11
• The DENSE trial showed a reduction in interval cancer rates from 5.0 to 2.5 per 1000 screenings with MRI 9, 10, 11

Important Nuances Regarding the Evidence

• The U.S. Preventive Services Task Force concludes that current evidence is insufficient to recommend a specific screening strategy for women with dense breasts, but the DENSE trial demonstrated a significant reduction in interval cancers with MRI 9, 10, 11
• Annual screening reduces mortality by 40% compared to biennial screening in women aged 40-84, with particular importance for women with dense breasts due to reduced mammography sensitivity 9, 10

Breast Imaging Guidelines for Dense Breast Tissue and Young Women

Dense Breast Tissue Considerations

• Approximately 43% of women aged 40-74 years have heterogeneously or extremely dense breasts, which increases breast cancer risk and decreases mammographic sensitivity 13, 14
• Dense breast tissue increases breast cancer risk with a relative risk of 1.23-1.30 and decreases mammographic sensitivity from 87% in fatty breasts to 63% in extremely dense breasts 14, 15
• The American College of Radiology recommends considering supplemental screening for women with dense breasts, with MRI being superior to ultrasound for supplemental screening in dense breasts 16, 17

Screening Recommendations

• The American College of Radiology recommends annual mammography as the primary screening tool, with supplemental MRI considered for high-risk women or those with extremely dense breasts 15, 16, 17
• Ultrasound may be considered as an alternative to MRI when MRI is contraindicated, unavailable, or unaffordable 17

Risk Stratification and False-Positive Burden

• Risk stratification using validated models is essential before recommending supplemental screening, as dense breast tissue alone does not justify supplemental screening 13, 14
• The cumulative probability of false-positive results over 10 years of annual screening in women with extremely dense breasts is 69% 13