For most women over the age of 40, an annual mammogram or screening with tomosynthesis is sufficient to monitor for breast cancer. For those women with a high risk of developing the disease, or with dense breasts, alternative imaging technologies, including breast MRI, are regularly used in addition to mammography. Technologies such as molecular breast imaging (MBI) and contrast-enhanced mammography are also emerging as adjunctive screening tools, though many clinicians remain concerned about the radiation exposure associated with nuclear breast imaging.

Dr. Maxine Jochelson, director of radiology at Memorial Sloan Kettering’s Breast and Imaging Center, notes that in 2007, the American Cancer Society recommended that women at greater than 20 percent lifetime risk of breast cancer receive annual MRI screening in addition to yearly mammography This includes women with a genetic mutation, such as the BRCA1 or BRCA2 gene, a very strong family history or those who have been treated with radiation therapy in the chest area. There is also concern that women with the BRCA gene might be more sensitive to radiation. “Research demonstrates that we may be able to eliminate mammograms in some of these women, especially for women under 40,” Jochelson says.


Dr. Debra Monticciolo, chair of the American College of Radiology (ACR) Commission on Breast Imaging and section chief of breast imaging at Baylor Scott & White Health in Temple, Texas, notes that in her practice mammography and MRI are alternated every six months for those in the high risk screening program. MRI techniques have become faster and resolution has improved over the last several years, with the switch from 1.5T to 3T scanning, and clinicians are experimenting with 7T. In Europe, clinicians are testing an abbreviated protocol that produces a limited number of pictures, Monticciolo says. The hope is that the shorter the scan time, the less expensive the exam.

“We’re considering whether to offer it here,” Monticciolo says. “Right now, our scan time is probably 15 to 20 minutes, while the abbreviated technique is three to four minutes. If we can lower costs by decreasing scan time, we can make the exam more accessible to the women who need it.”

‘Poor person’s MRI’
For women who are not mutation carriers, contrast-enhanced diagnostic mammography (CEDM) may be an alternative to more expensive MRI exams, especially for facilities without access to MRI equipment. There is ongoing research evaluating this. Jochelson calls this technology, which received FDA clearance in 2011, the “poor person’s MRI.” In contrast-enhanced mammography, two sets of images are obtained at a low- and high-energy level, after the injection of iodinated contrast, the same contrast used for CT scans. Processing of the two images yields a contrast image, which may show a cancer otherwise hidden in the breast. The low energy image is a regular mammogram. GE, Hologic and Siemens produce equipment.

“I’m sitting in a hospital with 13 MRIs,” Jochelson says. “Some places have none.” Moore County Hospital District in Dumas, Texas, is one such place. The rural facility doesn’t have MRI for breast imaging, but uses contrast-enhanced mammography for almost all recall exams, when a patient is recalled for an abnormal finding on a screening mammogram, says Dr. Sean Leong, the director of radiology. “It’s helped my practice so much in differentiating normal [tissue] from cancer,” Leong says. “It’s cut down the number of false positives in the patient population in my practice considerably.”

In Leong’s practice, contrast-enhanced mammography has replaced mammographic spot compressions to differentiate superimposed breast tissue from cancer. “There are a lot of questions associated with spot compression diagnostic mammography as only part of the breast is visualized: ‘Is the density there or not there? Did I squeeze that density out of my field of view? Did I even image the right spot?’ “ Leong says. “With CEDM, the entire breast is imaged and concerns that we have with spot compression about not imaging the necessary lesion are laid to rest.”

Before Leong’s practice used contrast enhanced mammography, all new indeterminate breast microcalcifications discovered by screening mammography were biopsied. “Approximately 80 to 90 percent of indeterminate calcifications are benign and 10 to 20 percent are malignant, so our surgeon was biopsying a lot of benign tissue that way,” Leong says. Now, with contrast-enhanced mammography, if there is no enhancing tissue associated with the calcifications, Leong and the other physicians in his practice follow them as if they are probably benign, with a diagnostic mammogram in six months and then subsequent annual screening with mammography.

A recent study at Chang Gung Memorial Hospital and Medical College of Chang Gung University in Taiwan, published in Diagnostic Imaging Europe last November, showed that contrast-enhanced mammography was more sensitive and more specific than MRI in evaluating indeterminate breast calcifications for malignancy.

While contrast-enhanced mammography is as sensitive but more specific than MRI, according to Leong, it is a newer technology and not as established as MRI.

A weakness of contrast-enhanced mammography, just as with conventional mammography, is that lymph nodes in the axilla are not completely visualized because it is difficult to pull the tissue in the axilla into the mammogram, according to Leong. “I ultrasound the axilla for all positive CEDM studies to completely evaluate the axilla for abnormal lymph nodes,” Leong says. “We have found several cancerous lymph nodes in the axilla that were not seen by CEDM or mammography.” Besides a lack of expensive MRI equipment, facilities also find it difficult to get pre-approval for MRI exams from insurance companies. “If [contrast-enhanced mammography] had come out first, I think it would have been hard for MRI to make a go of it,” Leong says.

MBI in place of MRI
Molecular breast imaging has also emerged as an alternative to MRI for women with dense breasts. Researchers at the Mayo Clinic published a study last year in the American Journal of Roentgenology that showed using molecular breast imaging detected nearly four times as many invasive cancers as digital mammography in women with dense breast tissue.

The ProMedica Breast Care radiology practice in Toledo, Ohio, recommends a supplemental MR scan for patients with a lifetime risk of at least 20 percent for developing breast cancer and who have dense breast tissue. But, for non-high-risk patients with dense breasts, or for those women who can’t undergo MRI because of a pacemaker or because they suffer from claustrophobia, they recommend screening with MBI. Ohio is one of more than two-dozen states with a breast density notification law, which requires physicians to notify women who have dense breast tissue.

ProMedica has Gamma Medica’s LumaGEM MBI system, which uses the technetium-99m sestamibi radiopharmaceutical and employs a dual-head digital detector and a special collimator. Dr. Robin Shermis, medical director of ProMedica Breast Care, says data in a paper he authored with others that was recently accepted by the American Journal of Roentgenology show that screening with MBI is capturing eight additional cancers per 1,000 women screened and has a sensitivity and specificity that approaches MRI. MBI is also a fraction of the price of an MRI and slightly more than a tomosynthesis examination, he says.

MBI uses 6 to 8 millicuries, about four times the dose from a digital mammogram and twice the dose of tomosynthesis and 2D mammography together, according to Shermis. For perspective, however, Shermis says the dose used is below background radiation levels and the benefits far exceed screening breast ultrasound. The newer technology of MBI also provides a much lower dose than the old breast specific gamma imaging (BSGI) examination of years ago, he says.

Mayo Clinic researchers are currently working to bring the dose down further and Gamma Medica is working on software and camera enhancements that would make it even lower, says Philip Croxford, the company’s president and CEO. “It’s a valuable new modality,” Croxford says. “It’s not for everyone, but it has enormous benefit when catching cancer.” Concerns about radiation dose still remain for some clinicians. “Manufacturers have done a lot to bring the dose down,” says Monticciolo of the ACR’s Commission on Breast Imaging. “The problem with nuclear medicine is that you’re giving the dose to the whole body. When you’re talking about using it as a screening tool, you can’t give that dose year after year. I think the dosage is the main limiting factor.”

Jochelson, of Memorial Sloan Kettering, agrees. “While nuclear breast imaging is able to detect cancers not seen on mammography, they find fewer cancers than MRI and unfortunately expose patients to more radiation than the other breast imaging tests,” Jochelson says. “Work is being done to lower the dose of radiation, but until that is complete, this type of imaging should not be done for yearly screening.”

Shermis says that while concerns about radiation dose persist, the newer levels need to be understood by referring physicians and patients and weighed against the importance of detecting cancers earlier. “We try to minimize dose in an effort to produce concrete benefits,” Shermis says. “Everything is a risk/benefit analysis and the vast majority of our patients understand the decision.”