MRI for Breast Cancer Screening? Depends on Your Patient

Mammography versus magnetic resonance imaging (MRI) has been a long-standing debate among industry leaders. The general consensus today, however, is while both tests effectively detect breast cancer and can work hand-in-hand, mammography is still indispensable.

According to the American Cancer Society, each year brings 1.3 million new breast cancer diagnoses, and catching these incidents early is critical to saving lives. While mammography has sliced the associated death rate by 30 percent since 1990, 465,000 women still die each year.

But breast imaging isn’t about choosing one scan over another, said Mitchell Schnall, MD, a Hospital of the University of Pennsylvania radiologist. Instead, you should focus on using both techniques correctly to identify cancers earlier when they’re smaller and potentially more treatable.

“We shouldn’t talk about MRI or mammography - they’re different modalities with different roles,” Schnall said. “Mammography is for general patient screening, and we use MRI to screen our high-risk patients. Their roles are complementary. The discussion should never be which one do we do.”

And the screenings aren’t interchangeable, experts said.

“Mammography is the backbone of how we diagnose breast cancer,” said David Dershaw, MD, a radiologist with Memorial Sloan-Kettering Cancer Center. “There are situations where MRI can add information we can’t get from mammography, but it can’t be a replacement.”

The Plus Side to Mammography

As a low-dose technology, mammography isn’t perfect. It can produce false positives and lead to additional scans, exposing patients to increased radiation. Industry leaders agree it’s a constant struggle to balance the desire to avoid false positives with the need for increased sensitivity to produce clearer images, Schnall said.

Even so, mammography is the most widely used and easily accessible screening method with nearly 10,000 mammography scanners nationwide. It’s also the technique women trust most to catch existing or developing disease. According to a September American College of Radiology (ACR) survey, 86 percent of women over age 40 report undergoing an annual scan, and nearly 90 percent believe mammograms help maintain their good health.

Scientific evidence mostly supports that belief. A 2007 New England Journal of Medicine study found that MRI pinpointed only 3.1 percent more cancers than mammography.

As a diagnostic tool, mammography is good at identifying carcinoma in situ, an early-stage breast cancer that shows no evidence of metastasis, Dershaw said. It’s also more affordable for patients to choose mammography over MRI. Based on ACR data, MRIs are approximately 10 times more expensive.

“To replace mammography with MRI - a test that costs between $1,000 to $1,500 per screening - just doesn’t make sense,” he said.

When MRI is Better

Although radiologists point to mammography as the go-to screening, especially for early-stage disease, MRI is superior for women who are at high risk for developing breast cancer. It’s also preferable in situations where the patient might have a rare form of the disease.

Existing research supports using MRI with women who have at least a 20 percent to 25 percent lifetime risk of developing breast cancer, Schnall said, especially those with the BRCA 1 or BRCA 2 genetic mutation. Additionally, since MRI uses a magnet rather than radiation to image the breast, it’s the preferred screening for women who’ve received chest wall radiation during previous cancer treatments.

In cases of rare cancers, MRI is essential to catching the disease, Dershaw said. For example, MRI outpaces mammogram in pinpointing invasive lobular carcinoma, a breast cancer that strikes the milk ducts and doesn’t present as a lump.

“In less common situations, MRI is really spectacular,” he said. “If a woman has cancer in the lymph nodes or if a cancer has been confirmed but a mammogram can’t find it in the breast, MRI can succeed. MRI locates roughly 85 percent of these cancers.”

This modality also helps providers determine how much of the breast is affected by the cancer. Scan results can directly impact any surgeries a woman has.

“The imaging can determine surgical procedures,” Dershaw said. “An MRI can show whether it will be possible to conserve any of the breast tissue or if a full mastectomy is warranted.”

MRI is also the choice screening method for women with prior breast cancer diagnoses, as well as for younger women who have dense breast tissue, said Priscilla Slanetz, MD, MPH, director of breast imaging research and education at Beth Israel Deaconess Medical Center.

Screening Guidance for You and Your Patient

The ACR published mammography guidelines in early 2010 and added MRI guidance with the launch of the Breast Magnetic Resonance Imaging Accreditation Program. Now, most breast imaging centers are rushing to meet the January 2012 voluntary accreditation deadline. The program will set MRI quality standards, as well as evaluate personnel and equipment performance.

The ACR also recommends you alternate between mammography and MRI screening every six months in high-risk cases. While no evidence exists to support this strategy, Slanetz said the goal is to catch cancers that pop up between annual screenings.

You should also be able to counsel patients on their true lifetime breast cancer risk, Schnall said. In recent years, he said he’s been pleased that more continuing medical education courses offer instruction on how to accurately determine risk.

“Women aren’t good at determining their risk. They dramatically overestimate their likelihood,” he said. “You have to be prepared to not only be the radiologist, but to be their primary care doctor, as well. And, it’s a role I think we’re qualified to take on.”