MRI in breast cancer screening, diagnostics up
Data underscore MRI value, but there are limitations
The value of magnetic resonance imaging (MRI) in helping clinicians to better assess the size and extent of known breast cancers is well established. However, the use of MRI as a screening tool in women at high risk of breast cancer is now on the increase as well, particularly since April 2007, when the American Cancer Society (ACS) unveiled guidelines recommending the use of MRI as a screening tool in this subset of women.
"The increase is appropriate as we have seen more scientific studies that show the benefit of breast MRI to patient care," explains Valerie Jackson, MD, FACR, who is chairman of the Department of Radiology at Indiana University School of Medicine in Indianapolis. For example, work published by Constance Lehman, MD, PhD, professor of radiology at the University of Washington School of Medicine in Seattle and director of breast imaging at the Seattle Cancer Care Alliance, and colleagues showed that MRI did a better job of detecting cancer in women at high risk for the disease than ultrasound or mammography.1
There are problems with MRI, however, not the least of which is cost. Imaging programs typically bill patients or their insurers $2,000 or more for the exam, including professional fees, although they are often reimbursed less than the stated charge. Further, while most hospitals and freestanding radiology centers have MR capabilities, most breast imaging centers do not, according to Jackson. The reason is that they don't have the financial resources or the case volume to justify the expense of buying an MR unit specifically for breast cancer, she says, and obtaining reimbursement can be an issue as well. "It depends on the carrier and the patient history," says Jackson. "We are finding some problems with reimbursement for screening MRI for high risk women, even though this is recommended by the ACS."
Nonetheless, some hospital-based imaging centers that did not have MRI breast imaging capabilities in the past are now making the investment. Jennifer Brewington, BSN, MSN, director of outpatient health for women and children at Huntsville (AL) Hospital for Women and Children, says, "We have been following this technology and felt that after our conversion to digital mammography [two years ago], that this would be the next tool that we would add to our arsenal for diagnostics. With the release in April [2007] of the ACS guidelines for the use of MRI in screening and diagnostics, our feelings were confirmed that now was the time to proceed with this technology."
MRI complements mammography
Radiologists agree that MRI offers important advantages in some cases. However, a significant drawback is that it prompts a high rate of unnecessary biopsies. There is no question that other imaging methodologies work better in some cases, according to Richard Lovett, MD, radiation oncologist at Rutland (VT) Regional Medical Center, who has conducted research into MRI of the breast.
"There are some early cancers that are detected better on mammography because they have these micro-calcifications that are just very subtle, and the resolution of MRI is not quite [good enough] so that we can see these small cancers that well," he says. "I would say the combination of the two [mammography and MRI] is definitely better than either one alone. They complement each other, but neither one replaces the other."
In fact, with good quality mammography and ultrasound, Jackson suggests that relatively few patients need to undergo breast MRI. "Ultrasound is faster, less expensive, and more available than MR, [although] the role of ultrasound in screening for breast cancer remains controversial and not a standard of care," she says.
Lovett agrees that the role of MRI in screening for breast cancer should be limited to women at high risk for the disease at this point, and his center has established its own specific guidelines in this regard. "The high-risk group that we have defined includes women who have a personal history of breast cancer, women who have a strong family history in first-degree relatives of breast cancer, and women who have indeterminate mammograms," says Lovett, noting that the center recommends that these women undergo breast MRI every two years. "In women with BRCA1 or BRCA2, we have been advocating for a yearly MRI scan," he says.
More recently, Lovett's research has focused on establishing the value of MRI in women who already have been diagnosed with breast cancer. At the annual scientific meeting of the American Society for Therapeutic Radiology and Oncology in November, Lovett presented data showing that MRI is a more accurate predictor of lesion size than mammography. His study involved the cases of 138 women, all of whom underwent an MRI scan before undergoing surgery. According to Lovett's findings, MRI accurately predicted lesion size 86% of the time compared to mammography, which accurately predicted lesion size just 56% of the time.
Lovett stresses that this information is important in helping surgeons determine whether the best course of action is local removal of the lesion or mastectomy. "That is where I see MRI as helping out," he says. "MRI will detect other lesions within the same breast, and it will show the size a little bit more true than the mammogram does."
Reference
- Lehman C, Isaacs C, Schnall M, et al. Cancer yield of mammography, MR, and US in high-risk women: prospective multi-institution breast cancer screening study. Radiology 2007; 244:381-388.
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