Other breast imaging modalities include MRI and ultrasound. MRI is generally reserved for those found by risk assessment to have an elevated risk of breast cancer. Again, while dense breasts are a cancer risk factor, not all women with dense breasts are at increased cancer risk. MRI is associated with an approximately 10-20% false positive (false alarm) rate and there are possible concerns related to the need for gadolinium, a heavy metal intravenous contrast.
The use of supplemental screening ultrasound has become more common. Supplemental ultrasound can find 0-5 additional cancers (versus mammogram alone) per 1000 studies. However, it is associated with an approximately 20-30% false positive rate, and an increased rate of benign (non-cancerous) biopsies and recommendations for follow up study. Because ultrasound was never designed as a full-breast screening tool, insurance may not cover the exam and recommended follow up. There are no studies demonstrating that cancer outcomes are improved using supplemental screening ultrasound.
It is important to realize that there is no perfect imaging technique for dense breasts – all available modalities have the potential to miss cancer. My recommendation is that women speak to their doctors and ask questions. Ask if your breast tissue is dense, how density impacts your breast cancer risk, and if additional testing is recommended for you.
Dr. Attai was one of the physicians invited to testify before the California Legislature in support of SB 1538, which was eventually signed by Governor Brown, requiring that imaging facilities in California inform women if they have dense breasts on mammography.
Updated January 31, 2022