MRI of the Breast on the Rise

In the first half of 2008, the number of patients undergoing magnetic resonance imaging (MRI) of the breast increased 23% over the same period in 2007, according to a newly released imaging market guide from Arlington Medical Resources. The revised cancer screening guidelines published by the American Cancer Society in 2007 may be partially responsible for the increased use of MRI. The guidelines recommended using MRI to screen women in specific risk groups, such as those with a strong family history of breast or ovarian cancer.

This increase does not surprise George Autz, MD, director of breast MRI services at South Nassau Communities Hospital’s Complete Women’s Imaging Center in New York. Dr. Autz said that he expects MRI of the breast to continue increasing over the next several years. “More patients are being appropriately recognized as qualifying for and benefitting from breast MRI. As clinicians and radiologists recognize the usefulness of the examination, then utilization will increase.”

that he expects the growing use of MRI in select patients to result in fewer false negative screening tests, which means fewer needle biopsies. He also predicted that MRIs would decrease the rate of a missed diagnosis, picking up tumors than mammography or clinical examinations may have missed.

William Dunn, MD, a radiation oncologist at West Michigan Cancer Center in Kalamazoo said

Dr. Dunn said that to date, campaigns to increase awareness of the usefulness of MRI in screening have likely not played much of a factor in their expanding use. “I don't think there is increased awareness of prevention in the general population or even with clinicians,” he explained. “I think they know about breast MRIs but may be hesitant to order them because not enough of them are aware of the guidelines.”

Selective Screening

It is important to use MRI responsibly as a screening method. “Patient selection is very important,” cautioned Dr. Autz. He pointed out that breast MRI, like other screening tests, is not perfect and false positives remain a concern. He suggested false positives were substantially more likely to occur in patients without appropriate indications for the examination.

Dr. Dunn concurred and said clinicians should follow he American Cancer Society’s screening guidelines. He explained that the value of MRI as a screening method comes from its sensitivity, specificity, and negative predictive value. Sensitivity refers to how good the test is at picking up a diagnosis; too many false negatives decrease the sensitivity rating. Specificity indicates how good the test is at weeding out true negatives from false positives. “Too many false positives mean more unnecessary procedures,” Dunn explained. The negative predictive value refers to a physician’s confidence level in telling a patient that he or she is 99% that the patient is disease-free.

Dr. Dunn said that studies of breast MRIs indicate a negative predictive value of 85% to 99%, which he described as “good,” and added “That means you can feel better about telling your patient she has no disease.” He noted that because MRI is very sensitive, the positive predictive value ranges from 25% to 50%, which he cautioned could lead to unnecessary breast procedures. “To limit this,” he said, “referring doctors should be very selective and use the ACS guidelines. I think the balance, thanks to the ACS, has been planned ahead of time.”

Community Oncologist’s Role

Dr. Dunn said there are additional reasons besides the American Caner Society guidelines to obtain breast MRIs. He discussed an article in the New England Journal of Medicine (March 29, 2007) that showed MRI was better than mammography at picking up tumors in the contralateral breast for women who already have a diagnosis of breast cancer and are at higher risk for such tumors.

Dunn listed other reasons for oncologists to order MRI of the breast:

• MRI is a suggested method for monitoring patient response to neoadjuvant treatment;
• Surgical scars can harbor disease, and MRI may help distinguish recurrence from scar tissue;
• To identify any remaining disease in patients whose pathology findings show close margins and multi-focal lobular cancer;
• To identify tumors hiding in a contralateral breast in patients with lobular cancer, which tends to be bilateral;
• In patients with axillary lymph nodes and negative mammograms, MRI can help find the occult primary;
• MRI can help discern whether surgical excision was complete in patients with fascial involvement or tumors lying proximal to the chest wall, possibly sparing the patient an unnecessary total mastectomy; and
• MRI may be useful in patients with breast implants or tissue expanders, which sometimes block the view of classical mammograms.

Dr. Autz advised community-based oncologists to “work in conjunction with their radiologist to determine which patients would benefit from breast MRI as an additional examination,” such as patients who have undergone lumpectomy and radiation treatment or who have unclear mammograms or complex scarring.

Dr. Dunn expressed optimism about the upswing in breast MRI, theorizing that it could help many patients avoid unwanted procedures, including biopsies, lumpectomies, and mastectomies. He also said he hoped it would increase the cure rate for patients with breast cancer. “With the proper use of this tool already in place, this will help us to catch breast cancer in these targeted cases at even earlier stages, ending up with what I feel may be at least a 10% to 20% increased chance for a cure.”

Ed Rabinowitz is a veteran healthcare reporter and writer. He welcomes comments at edwardr@frontiernet.net.