Breast Cancer Screening - Magnetic Resonance Imaging

Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) has been shown to detect cancers not visible on mammograms. The chief strength of breast MRI is its very high negative predictive value. A negative MRI can rule out the presence of cancer to a high degree of certainty, making it an excellent tool for screening in patients at high genetic risk or radiographically dense breasts, and for pre-treatment staging where the extent of disease is difficult to determine on mammography and ultrasound. MRI can diagnose benign proliferative change, fibroadenomas, and other common benign findings at a glance, often eliminating the need for costly and unnecessary biopsies or surgical procedures. The spatial and temporal resolution of breast MRI has increased markedly in recent years, making it possible to detect or rule out the presence of small in situ cancers, including ductal carcinoma in situ.

However, breast MRI has long been regarded to have disadvantages. For example, although it is 27–36% more sensitive, it has been claimed to be less specific than mammography. As a result, MRI studies may have more false positives (up to 30%), which may have undesirable financial and psychological costs. It is also a relatively expensive procedure, and one which requires the intravenous injection of gadolinium, which has been implicated in a rare reaction called nephrogenic systemic fibrosis. Although NSF is extremely uncommon, patients with a history of renal disease may not be able to undergo breast MRI. Further, an MRI may not be used for screening patients with a pacemaker or breast reconstruction patients with a tissue expander due to the presence of metal.

Proposed indications for using MRI for screening include:

• Strong family history of breast cancer
• Patients with BRCA-1 or BRCA-2 oncogene mutations
• Evaluation of women with breast implants
• History of previous lumpectomy or breast biopsy surgeries
• Axillary metastasis with an unknown primary tumor
• Very dense or scarred breast tissue

In addition, breast MRI may be helpful for screening in women who have had breast augmentation procedures involving intramammary injections of various foreign substances that may mask the appearances of breast cancer on mammography and/or ultrasound. These substances include silicone oil and polyacrylamide gel.