Breast MRI

Contrast-enhanced magnetic resonance imaging (MRI) is a medical imaging test that uses very strong magnets and radio waves to create images of the body. Breast MRI requires injection of gadolinium-based contrast agent into a vein in the arm to evaluate the breast tissue (Fig. MRI-1), looking at both anatomy and blood flow patterns. Normal tissue, cancers, and benign (noncancerous) findings can enhance (light up) on MRI. MRI is the most sensitive breast cancer screening modality and is not affected by breast density. MRI is recommended in addition to mammography to screen women at high risk for breast cancer. MRI is also commonly used to assess the local extent of disease to help stage women with newly diagnosed breast cancer. MRI staging is particularly helpful for women with invasive lobular carcinoma (ILC) [1] as it is often underestimated on mammography and ultrasound [2-5].

For breast MRI, a patient lies face down on a special table with her breasts positioned in an opening called a coil that improves the image quality (Figs. MRI-2, -3). The exam takes place in the “tunnel” of the MRI scanner which makes loud “tapping” noises for several minutes at a time while the imaging is taking place. After an initial set of images has been obtained, a small amount of gadolinium-based contrast agent is injected into a vein in the arm. It is important for the patient to lie still as any motion can reduce image quality and make the images hard to interpret. The usual breast MRI examination takes about 25 minutes.

Abbreviated MRI

A shorter technique, called “abbreviated MRI”, can achieve similar performance when used for screening [6, 7] and may also be offered at some sites.  An abbreviated MRI takes fewer images and lasts only about 10 minutes. For individuals with claustrophobia, a sedative can be requested from the referring provider that can be taken 30 minutes prior to the MRI examination. A large multicenter 2020 study [8] compared screening abbreviated MRI to digital breast tomosynthesis in nearly 1500 patients with dense breasts and showed that abbreviated MRI found an additional 9/1000 cancers compared to tomosynthesis (15.2/1000 for abbreviated MRI versus 6.2/1000 for tomosynthesis) in the first year of screening.  A smaller, but persistent benefit from adding MRI was identified in the second year as well [9].

Even after screening with mammography/tomosynthesis and ultrasound, screening breast MRI reveals an average of 10 additional cancers per thousand women screened (16-17 with the first MRI and 6-7 per year thereafter) [6, 8, 10-13]. The cancer-detection benefit is seen across all breast density categories and for women at average or high risk [10]. MRI detects more cancers than any other screening test and is recommended every year for women who are at high risk for breast cancer, including women with a personal history of breast cancer and dense breasts or diagnosis by age 50 [14]. Many women with dense breasts and a family history of breast cancer or prior biopsy with atypia will meet high-risk criteria (estimated lifetime risk of more than 20%) for screening MRI [15]. For women with dense breasts and no other risk factors who desire supplemental screening, the American College of Radiology recommends MRI [14]. Studies have suggested a slight improvement in cancer detection when MRI is performed on an alternating six-month basis with mammography (e.g. mammogram in January and MRI in July) [16]. There is no benefit to screening US in women having screening MRI [17].

In the DENSE trial in the Netherlands, women with extremely dense breasts and negative mammograms were randomized so that half of them were offered an MRI.  In the women who had MRI, there were many fewer symptomatic (interval) cancers that developed between screens and much greater detection of early breast cancer compared to women who had a mammogram alone [12].  As expected, false positives decreased in the second round of MRI screening [13]. These results prompted the European Society of Breast Imaging to recommend screening MRI every 2-4 years among women ages 50-74 with extremely dense breasts [18].

Breast MRI will find more areas of concern than either a mammogram or ultrasound. Some of those “finds” will be cancer, but more than half will not (known as a “false positive”). The false positive rate is highest on the first or baseline MRI exam as the radiologist has no prior MRIs for comparison.  On subsequent MRIs, the false positive rate decreases. MRIs should be interpreted in conjunction with any other available breast imaging studies, including mammography and ultrasound, as well as knowledge of any prior biopsy results. The facility should also be able to perform an MRI-guided biopsy or have a formal arrangement to refer patients to another facility that has MRI biopsy capability. All facilities accredited in breast MRI by the American College of Radiology should meet these requirements.

MRI cannot be performed in women who have certain metal implants such as a pacemaker or spinal fixation rods. Contrast-enhanced MRI should not be performed if the patient is pregnant. Not all patients can receive gadolinium contrast agent due to allergy or kidney disease. Women with claustrophobia may not be able to tolerate MRI. The positioning can be difficult for some patients with neck problems, obesity or breathing issues. Repeated contrast-enhanced MRIs, including non-breast MRIs, can cause the accumulation of gadolinium in the brain [19], but at this time this is not known to have any harmful effects. There is more accumulation of gadolinium with certain contrast agents that are no longer in widespread use [20].*  For women who cannot undergo breast MRI, contrast-enhanced mammography, molecular breast imaging, or possibly ultrasound may be acceptable alternatives if available [14, 21].

* “Linear” contrast agents “leak” more gadolinium and therefore show greater accumulation of gadolinium in the brain than “caged” or “macrocyclic” agents. Linear agents include gadopentetate dimeglumine [Magnevist], gadodiamide [Omniscan], and gadoversetamide [OptiMARK]. Macrocyclic agents include gadoterate meglumine [Dotarem], gadobutrol [Gadavist], gadoteridol [ProHance] and gadopiclenol [Vueway].

Latest update: 1/24/24