For a patient with very dense breasts, classified as D, should they have an MRI and bilateral ultrasound or an MRI and bilateral mammogram?

Breast Cancer Screening for Patients with Extremely Dense Breasts (BI-RADS D)

For patients with extremely dense breasts (BI-RADS category D), MRI with bilateral mammogram is the recommended screening approach rather than MRI with bilateral ultrasound.

Rationale for MRI with Mammography

Understanding Dense Breast Tissue

• Dense breast tissue (BI-RADS D) significantly reduces mammography sensitivity from 87% in fatty breasts to only 63% in extremely dense breasts 1
• Dense breasts are an independent risk factor for breast cancer development, with relative risk of 1.23-1.30 compared to average breast density 1

Evidence Supporting MRI with Mammography

1. Complementary Detection Methods:

   • Mammography/Digital Breast Tomosynthesis (DBT) remains the foundational screening tool for all women, including those with dense breasts 1
   • MRI has the highest sensitivity (94.6%) for breast cancer detection compared to mammography (54.5%) and ultrasound (67.2%) 2
   • The combination of mammography and MRI provides the most comprehensive screening approach

2. Clinical Outcomes:

   • The DENSE trial showed that supplemental MRI screening in women with extremely dense breasts reduced interval cancer rates from 5.0 to 2.5 per 1000 screenings 3
   • Among women who actually underwent MRI in this trial, interval cancer rate was only 0.8 per 1000 screenings 3

Screening Algorithm for Extremely Dense Breasts

For Average-Risk Women with Extremely Dense Breasts:

• Digital Breast Tomosynthesis (DBT) is usually appropriate as the primary screening tool 1
• Consider supplemental MRI every 2-4 years as recommended by the European Society of Breast Imaging 4

For Intermediate-Risk Women with Extremely Dense Breasts:

• DBT is usually appropriate as the primary screening tool 1
• Consider supplemental MRI based on additional risk factors 1

For High-Risk Women with Extremely Dense Breasts:

• Both DBT and MRI with contrast are usually appropriate and complementary 1
• Annual surveillance with MRI and mammography is strongly recommended 1

Why Not MRI with Ultrasound?

While ultrasound is sometimes used as a supplemental screening tool for dense breasts, the evidence favors the MRI-mammography combination for several reasons:

1. Superior Detection Capability:

   • The sensitivity of combined mammography and MRI reaches 100%, compared to only 44-48% for mammography and ultrasound combined 1
   • MRI detects more invasive carcinomas (71%) than other modalities 1

2. Reduced False Negatives:

   • Ultrasound has limited sensitivity (67.2%) compared to MRI (94.6%) 2
   • MRI is particularly valuable in dense breast tissue where mammographic sensitivity is reduced

Important Considerations

• False Positives: MRI has a higher false positive rate (79.8 per 1000 screenings) 3, which must be balanced against improved cancer detection
• Cost and Access: MRI is more expensive and may have limited availability, though abbreviated MRI protocols may help address these concerns 1, 5
• Radiation Exposure: The combination of MRI (no radiation) with mammography limits overall radiation exposure compared to other combinations

Conclusion

For patients with extremely dense breasts (BI-RADS D), the combination of MRI with mammography provides the most effective screening approach, offering superior sensitivity and the best chance for early cancer detection, which directly impacts morbidity and mortality outcomes.