The Pros and Cons of Breast MRI
Used as a supplemental tool to conventional testing, MRIs are exposing hidden breast tumors.

By Paul Engstrom

Leslie Stiles had a nagging sense she was “dodging the bullet,” given the four biopsies she underwent over about 20 years to determine if lumps in her breasts were cancerous.

Although the biopsy results always came back negative (the lumps were due to fibrocystic disease), Stiles’ dense breast tissue prompted her surgeon to recommend magnetic resonance imaging (MRI) in the fall of 1999 at Thomas Jefferson University Hospital in Philadelphia, which had recently begun using MRI on breasts.

This time, the magnetic field and radio waves of MRI detected something suspicious. After a follow-up ultrasound and tissue sampling with MRI-guided needle biopsy, the news wasn’t good. She ultimately received radiation and chemotherapy for stage 1 invasive ductal carcinoma in her right breast.

“I’m a very lucky woman,” says Stiles, executive director of the Pennsylvania Commission for Women, who has been cancer-free for nearly five years. “From my perspective, you have to look at the glass as being half full. I would advise MRI to as many people as can get it. It’s a gift.”

Still Experimental

Yet MRI for breast cancer isn’t likely to become a standard, widespread screening tool like mammography anytime soon. For now, as research on the procedure continues, clinicians are using it as a supplemental tool to further investigate possible malignancies that appear during physical exam, mammography or ultrasound. In patients like Stiles, dense breast tissue—which is particularly common in young women—can mask a small, dense cancerous growth. And family history or genetic predisposition may put them at higher risk for breast cancer.

Indeed, the test offers multiple benefits. For example, not only is it good at pinpointing the location and size of breast abnormalities, but it’s better than a physical exam or mammography in helping determine the extent of cancer or if there’s more than one lesion, says David A. Bluemke, MD, PhD, clinical director of MRI at Johns Hopkins University School of Medicine in Baltimore. And MRI’s three-dimensional images, compared to mammography’s two-dimensional imagery, are “very effective” for assessing tissue around breast implants, he says.

Because the sensitive test may show the true edges of a cancer, it can also sometimes guide treatment before surgery, indicate how extensive the surgery needs to be or help gauge whether radiation therapy will help, says Mitchell Schnall, MD, PhD, chief of MRI at the University of Pennsylvania Medical Center.

Still another bonus: Unlike the X-rays in mammography, MRI doesn’t expose women to radiation, too much of which can damage genetic material in cells.
Despite all these accolades, MRI hasn’t become a mainstream breast-screening method like mammography because the test, which typically takes 30 to 60 minutes, can cost at least 10 times as much as mammography—$1,000 or more, depending on geographic region, compared to $100-$150 for a mammogram.

In addition, the very sensitivity that makes MRI so valuable results in detection of more abnormalities than other tools, leading to a high rate of false-positives, or results that initially suggest cancer but in fact are benign. However, mammography, ultrasound and physical exam also generate false-positives, some experts note, arguing that those from MRI don’t occur at a significantly higher rate.

False-positives are a big problem because they mean needless anxiety for patients, says Frederick Kelcz, MD, associate professor of radiology at the University of Wisconsin-Madison Hospital. They can lead to unnecessary and unpleasant surgical procedures, such as biopsy or even prophylactic mastectomy, which entail risk and considerable expense. “A lot of things light up using MRI, but only some are cancerous,” Dr. Kelcz says.

On the other hand, tissue sampling using MRI-guided needle biopsy—a simple, low-risk procedure—can allay the anxiety women might otherwise feel about having a chunk of tissue surgically removed, which involves greater risk, discomfort and scarring.

But many clinicians lack the experience to accurately interpret the nuances of MRI breast results, and some insurers don’t cover MRI breast screening, although Blue Cross/Blue Shield Technology Evaluation Center and the American Cancer Society have endorsed it for high-risk women.

Finally, as Patricia Setser discovered, the test isn’t available in many smaller communities.

In late 2002, Setser, a 53-year-old high school band director and part-time school administrator in Raymore, Missouri, drove about 600 miles to the University of Arkansas for Medical Sciences in Little Rock to undergo MRI after mammography flagged a mass in her right breast.

Setser had good reason to be especially concerned. She had been “faithfully flunking” breast exams for about 10 years because of her dense breasts, has a family history of breast cancer and had a hysterectomy for uterine cancer in 2001. Only after Setser underwent an ultrasound-guided procedure in which fluid was extracted from a suspicious cyst in her left breast and analyzed, did she learn she was cancer-free.

Setser says the “incredibly clear” images from MRI gave her confidence that doctors were doing everything they could to rule out malignancy. With MRI, “You’re not guessing anymore,” she says. “You can see absolutely everything.”

Finding New Tools

MRI for breast screening gained attention in the early 1990s when clinicians were using the tool on women with known cancer, says Steven Harms, MD, Setser’s radiologist in Little Rock. “We started finding additional cancers that could not be seen any other way. We thought, ‘If we can see this well in people with cancer, maybe we could also use it for people without a history of cancer.’”

Today, while investigators debate whether MRI for breast screening should be routine in light of the emotional and economic toll of false-positives, three recent studies—at Memorial Sloan-Kettering Cancer Center in New York City as well as in the Netherlands and Germany—involving high-risk women suggest that it catches tissue abnormalities that mammography misses.

In the past dozen years or so, the same general-purpose MRI scanners used for evaluating the brain, heart and other soft tissues have been adapted to the needs of breast imaging to include special magnetic coils and equipment for taking tissue samples through a needle for biopsy. A new MRI scanner called Aurora goes a step further. Its magnet, the gear for biopsies and interventional therapy, the patient table and computerized imaging are tailored to the breasts.

But sophisticated technology has its limits. “Breast MRI is probably the most difficult MRI examination to perform well and interpret well” and requires “an incredible amount of analytical ability,” says Mark Novick, MD, medical director of the Manhattan East Breast Imaging Center in New York. “There are subtleties that can escape even the best-trained radiologist.”

For this reason, Dr. Novick and other experts recommend that, if possible, women undergo the procedure at centers where breast MRIs are the focus of highly experienced clinicians.

It’s also important, Dr. Novick says, that a medical facility is able to follow through on image findings by sampling tissue and confirming the results. If a facility can only perform the scan, an expert elsewhere may have to review the images and take samples, which in turn might lead to retesting—and to more delays and expense.

Breast screening with MRI isn’t for everyone. But the way Dr. Harms sees it, for women who can take advantage of this promising technology and who may have watched their mother or sister die of breast cancer, “having a negative exam is like having the weight of the world lifted off your shoulders.”